What is the fineness of the plug in the 1792 silver center cent?
CaptHenway
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Does anybody know? Has anybody ever shot an x-ray or whatever at the plug?
Numismatist. 50 year member ANA. Winner of four ANA Heath Literary Awards; three Wayte and Olga Raymond Literary Awards; Numismatist of the Year Award 2009, and Lifetime Achievement Award 2020. Winner numerous NLG Literary Awards.
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Interesting question...
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<< <i>What was the fineness of Martha Washington's silverware? >>
Gratuitous, but I'm glad he's paying attention. He knows the metal was melted to be recast. There goes your DNA evidence.
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Buy a Silver-Center with lab-verified Sally Hemings DNA. When it comes out of the MRI things will be clearer.
I'm predicting .925, but this is speculation. No actual paperwork (located (as of yet)) . . . .
My first guess would be .8925 fine. What is the fineness of other pattern coins in silver attributable to the creator(s) of these silver center cents?
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Properties of the Silver Center Cents
Voigt's plan toward a smaller one cent coin was ingenious, combining a silver plug valued at 3/4 cent with a copper planchet valued at 1/4 cent. The 1792 Mint Act specified that the one cent coin should have a weight of 264 grains of pure copper. A quarter cent of copper would weigh 66 grains.
The same Act specified that a silver dollar was to contain 416 grains of standard silver (89.24% silver, 10.76% copper), or 371.25 grains of pure silver, yielding 3.71 grains of pure silver per one cent. It is likely that the plug consisted of pure silver, having a weight of 2.78 grains.
The combination of copper and silver gives a theoretical weight of 68.78 grains. The actual recorded weights of four high-grade pieces are 67.5 grains, 69.9 grains, 70.5 grains, and 72.8 grains, for an average of 70.2 grains.
The Copper Planchet
We have known diameters for six different Silver Center cents: 22.4 mm, 22.4 mm, 22.5 mm, 22.5 mm, 22.6 mm, and 22.9 mm, with an average of 22.55 mm. We will use 22.4 mm as the theoretical diameter. By using the familiar formula using pi, the surface area of the planchet is 394.08 square millimeters.
Pure copper has a density of 8.94 gm/cc, equal to 0.138 grains per cubic millimeter. The theoretical weight of 66 grains, divided by the density, results in a theoretical volume of 478.26 cubic millimeters. Volume divided by surface area gives a theoretical thickness of 1.21 mm.
The copper planchet was approximately 22.4 mm diameter and 1.2 mm thick.
The Silver Plug
The volume, dimensions, and composition of the silver plug present a few problems. We have already determined that a plug of pure silver valued at 3/4 cent will weight 2.78 grains. Silver has a density of 10.49 gm/cc, equal to 0.1619 grains per cubic millimeter. Weight divided by density gives a theoretical volume of 17.17 cubic millimeters for the silver plug.
All known Silver Center cents retain a plug with a larger diameter on the obverse than on the reverse. That observation suggests a conical plug, rather than a cylindrical plug. We also know that the thickness of the copper planchet is 1.2 mm. Once the coin was struck, the plug will have the same thickness. The volume of 17.17 cubic millimeters divided by the 1.2-mm thickness yields a surface area of 14.31 square millimeters. Using the formula for the area of a circle, the theoretical radius is 2.13 mm, giving a diameter of 4.26 mm.
The theoretical diameter of the plug is much greater than found on known specimens. The conclusion is that the Silver Center cents were made with a smaller amount of silver for illustrative purposes only. Congressional approval was uncertain, so there was no reason to use the full amount of silver valued at 3/4 cent when a lesser amount would suffice. It is unlikely that anyone in Congress would have checked that closely. There is apparently no standard dimension for the silver plug in these coins, so variance between surviving specimens is likely.
It was to be 1/4 of the cent's value would be pure copper & 3/4 of the cent's value would be pure silver.
Don't know if anyone ever tested it since 1792, but I do know I didn't.
R.I.P. Bear
<< <i>As described for the Morris Specimen:
Properties of the Silver Center Cents
Voigt's plan toward a smaller one cent coin was ingenious, combining a silver plug valued at 3/4 cent with a copper planchet valued at 1/4 cent. The 1792 Mint Act specified that the one cent coin should have a weight of 264 grains of pure copper. A quarter cent of copper would weigh 66 grains.
The same Act specified that a silver dollar was to contain 416 grains of standard silver (89.24% silver, 10.76% copper), or 371.25 grains of pure silver, yielding 3.71 grains of pure silver per one cent. It is likely that the plug consisted of pure silver, having a weight of 2.78 grains.
The combination of copper and silver gives a theoretical weight of 68.78 grains. The actual recorded weights of four high-grade pieces are 67.5 grains, 69.9 grains, 70.5 grains, and 72.8 grains, for an average of 70.2 grains.
The Copper Planchet
We have known diameters for six different Silver Center cents: 22.4 mm, 22.4 mm, 22.5 mm, 22.5 mm, 22.6 mm, and 22.9 mm, with an average of 22.55 mm. We will use 22.4 mm as the theoretical diameter. By using the familiar formula using pi, the surface area of the planchet is 394.08 square millimeters.
Pure copper has a density of 8.94 gm/cc, equal to 0.138 grains per cubic millimeter. The theoretical weight of 66 grains, divided by the density, results in a theoretical volume of 478.26 cubic millimeters. Volume divided by surface area gives a theoretical thickness of 1.21 mm.
The copper planchet was approximately 22.4 mm diameter and 1.2 mm thick.
The Silver Plug
The volume, dimensions, and composition of the silver plug present a few problems. We have already determined that a plug of pure silver valued at 3/4 cent will weight 2.78 grains. Silver has a density of 10.49 gm/cc, equal to 0.1619 grains per cubic millimeter. Weight divided by density gives a theoretical volume of 17.17 cubic millimeters for the silver plug.
All known Silver Center cents retain a plug with a larger diameter on the obverse than on the reverse. That observation suggests a conical plug, rather than a cylindrical plug. We also know that the thickness of the copper planchet is 1.2 mm. Once the coin was struck, the plug will have the same thickness. The volume of 17.17 cubic millimeters divided by the 1.2-mm thickness yields a surface area of 14.31 square millimeters. Using the formula for the area of a circle, the theoretical radius is 2.13 mm, giving a diameter of 4.26 mm.
The theoretical diameter of the plug is much greater than found on known specimens. The conclusion is that the Silver Center cents were made with a smaller amount of silver for illustrative purposes only. Congressional approval was uncertain, so there was no reason to use the full amount of silver valued at 3/4 cent when a lesser amount would suffice. It is unlikely that anyone in Congress would have checked that closely. There is apparently no standard dimension for the silver plug in these coins, so variance between surviving specimens is likely.
It was to be 1/4 of the cent's value would be pure copper & 3/4 of the cent's value would be pure silver.
Don't know if anyone ever tested it since 1792, but I do know I didn't. >>
Wow! That is how numismatics is done. The description written up for the Silver Plug is awesome!
Now, about that silver purity question....
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<< <i>As described for the Morris Specimen:
Properties of the Silver Center Cents
Voigt's plan toward a smaller one cent coin was ingenious, combining a silver plug valued at 3/4 cent with a copper planchet valued at 1/4 cent. The 1792 Mint Act specified that the one cent coin should have a weight of 264 grains of pure copper. A quarter cent of copper would weigh 66 grains.
The same Act specified that a silver dollar was to contain 416 grains of standard silver (89.24% silver, 10.76% copper), or 371.25 grains of pure silver, yielding 3.71 grains of pure silver per one cent. It is likely that the plug consisted of pure silver, having a weight of 2.78 grains.
The combination of copper and silver gives a theoretical weight of 68.78 grains. The actual recorded weights of four high-grade pieces are 67.5 grains, 69.9 grains, 70.5 grains, and 72.8 grains, for an average of 70.2 grains.
The Copper Planchet
We have known diameters for six different Silver Center cents: 22.4 mm, 22.4 mm, 22.5 mm, 22.5 mm, 22.6 mm, and 22.9 mm, with an average of 22.55 mm. We will use 22.4 mm as the theoretical diameter. By using the familiar formula using pi, the surface area of the planchet is 394.08 square millimeters.
Pure copper has a density of 8.94 gm/cc, equal to 0.138 grains per cubic millimeter. The theoretical weight of 66 grains, divided by the density, results in a theoretical volume of 478.26 cubic millimeters. Volume divided by surface area gives a theoretical thickness of 1.21 mm.
The copper planchet was approximately 22.4 mm diameter and 1.2 mm thick.
The Silver Plug
The volume, dimensions, and composition of the silver plug present a few problems. We have already determined that a plug of pure silver valued at 3/4 cent will weight 2.78 grains. Silver has a density of 10.49 gm/cc, equal to 0.1619 grains per cubic millimeter. Weight divided by density gives a theoretical volume of 17.17 cubic millimeters for the silver plug.
All known Silver Center cents retain a plug with a larger diameter on the obverse than on the reverse. That observation suggests a conical plug, rather than a cylindrical plug. We also know that the thickness of the copper planchet is 1.2 mm. Once the coin was struck, the plug will have the same thickness. The volume of 17.17 cubic millimeters divided by the 1.2-mm thickness yields a surface area of 14.31 square millimeters. Using the formula for the area of a circle, the theoretical radius is 2.13 mm, giving a diameter of 4.26 mm.
The theoretical diameter of the plug is much greater than found on known specimens. The conclusion is that the Silver Center cents were made with a smaller amount of silver for illustrative purposes only. Congressional approval was uncertain, so there was no reason to use the full amount of silver valued at 3/4 cent when a lesser amount would suffice. It is unlikely that anyone in Congress would have checked that closely. There is apparently no standard dimension for the silver plug in these coins, so variance between surviving specimens is likely.
It was to be 1/4 of the cent's value would be pure copper & 3/4 of the cent's value would be pure silver.
Don't know if anyone ever tested it since 1792, but I do know I didn't. >>
Thanks for the reference!
TD
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XRF might reveal actual fineness.
Well, just Love coins, period.
<< <i>Britannia "standard" silver was .958 fine....
XRF might reveal actual fineness. >>
Please linkify the Wiki on .958 silver. Fascinating . . .
Now we'll need records of when Martha's Custis family silver was made. Dig on.....