Engelhard Prospector 'fails' Sigma Metalytics testing

astrorat

In a recent batch of Engelhard Prospectors I picked up, one of the rounds failed to be within specs according to my Sigma Metalytics. The culprit was a 1982 Engelhard Prospector that fell below range for 99.9% (pure silver), but was in the high range for 92.5% (sterling) and dead center for 96% (Britannia).

When a specific gravity test was done, the result was 10.51, which is spot on (pun intended) for pure silver. As an aside, this is not the first time I have had a pure silver bar or round 'fail' Sigma Metalytics, but pass the specific gravity test. There must be some impurities that remained in these bars and rounds from that era that mess with the resistance and throw off the Sigma Metalytics.

One more thing ... a big shout out to @mapleman as a bullion trading partner!

Edited for spelling ...

mapleman

@astrorat said:
In a recent batch of Engelhard Prospectors I picked up, one of the rounds failed to be within specs according to my Sigma Metalytics. The culprit was a 1982 Engelhard Prospector that fell below range for 99.9% (pure silver), but was in the high range for 92.5% (sterling) and dead center for 96% (Britannia).

When a specific gravity test was done, the result was 10.51, which is spot on (pun intended) for pure silver. As an aside, this is not the first time I have had a pure silver bar or round 'fail' Sigma Metalytics, but pass the specific gravity test. There must be some impurities that remained in these bars and rounds from that era that mess with the resistance and throw off the Sigma Metalytics.

One more thing ... a big shout out to @mapleman as a bullion trading partner!

Edited for spelling ...

Thanks @astrorat for the shout out. I could add a volume on this anomalous Prospector but @astrorat clearly illustrates the issues. I will ad FWIW that having tested it many times , when the round is room temp and after the sigma had been on for a bit of other testing, this prospector fell in to spec. It is the correct weight. I contacted ATE, sent pics,and was told "no reason to doubt" authenticity. They did mention some planchet issues in 82s which contributed to some softer strikes and die wear.

Enough from me. This is @astrorats post and btw, I'll gladly deal with him anytime.

1630Boston

I have also found that metal temperature is important for ASE's and the PMV

TwoSides2aCoin

I enjoy these public shoulder rubbing threads.

asheland

I wouldn't worry about that prospector.

astrorat

@asheland said:
I wouldn't worry about that prospector.

I am not worried at all. The Sigma Metalytics instrument is just a tool and is not infallible. When something 'fails' the Sigma, I use specific gravity to verify.

derryb

The OP's sigma reading is just outside the "acceptable" ban. When a metal is this close to "acceptable" it requires further sigma testing. Try flipping the coin, relocating it over the sensor, or use one of the bullion probes to measure. Normally fake bullion items will go off scale to the right or left showing a horizontal arrow.

Take note that thin bullion items such as $5 AGEs are tough to successfully measure. Recently had some $5 AGEs returned from a buyer because he didn't take the time to read the sigma manual concerning thin metal. When returned they tested good.

1630Boston

Thinner pieces can be measured using one of the smaller wands or by using the calibration disk.
The calibration disc is the coin sized metal piece with the Precious Metal Verifier (PMV) logo. Using
this disc with the main sensor, place your coin or bar on top of the sensor target and then place the
disc on top of the item you are testing. Make sure the calibration disc is directly above the sensor
circle.

astrorat

@derryb said:
The OP's sigma reading is just outside the "acceptable" ban. When a metal is this close to "acceptable" it requires further sigma testing. Try flipping the coin, relocating it over the sensor, or use one of the bullion probes to measure. Normally fake bullion items will go off scale to the right or left showing a horizontal arrow.

Take note that thin bullion items such as $5 AGEs are tough to successfully measure. Recently have some $5 AGEs returned from a buy because he didn't take the time to read the sigma manual concerning thin metal. When returned they tested good.

Yep ... I did the repositioning, however I did not use the probes on this round. When I had the same issues with some bars from the 1980s, I did use the probes as well with the same result.

The Sigma folks just passed off the bar as 'likely sterling.' They could not explain why the specific gravity indicated 0.999 and not 0.925.

Sigma 'retesting' may or may not work if the resistance reading is due to an impurity, despite the item being 0.999.

asheland

@derryb said:
The OP's sigma reading is just outside the "acceptable" ban. When a metal is this close to "acceptable" it requires further sigma testing. Try flipping the coin, relocating it over the sensor, or use one of the bullion probes to measure. Normally fake bullion items will go off scale to the right or left showing a horizontal arrow.

Take note that thin bullion items such as $5 AGEs are tough to successfully measure. Recently have some $5 AGEs returned from a buy because he didn't take the time to read the sigma manual concerning thin metal. When returned they tested good.

You need the wand for the small pieces...

GRANDAM

Try the .999 setting.

astrorat

@GRANDAM said:
Try the .999 setting.

I did. The 0.999 setting resulted in the bar further to the right of the brackets.

ricko

Interesting information about the Sigma equipment..... Most machines have certain quirks like this, and I would think the experts at the manufacturer could explain it best. Cheers, RickO

astrorat

@ricko said:
Interesting information about the Sigma equipment..... Most machines have certain quirks like this, and I would think the experts at the manufacturer could explain it best. Cheers, RickO

The explanation to me was that the bars I was testing must be not be 0.999. They told me the bars were probably sterling. I shared the specific gravity results, but they were dismissive. Oh well. The Sigma Metalytics is a nice tool, but it's just one tool.

topstuf

There were some reports in the mid 80's of problem Englhard 100 oz bars.
This is from my last explanation.
]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]

This information is from a mid-1980’s bulletin on Coinnet from TX21. (Don’t even know if they are still around.)

Their Info:
Altered Englehard Bar Test
The following instructions are to test Englehard extruded bars that may have been altered......Four bars have now turned up in this area and this test has been good on all bars.....Test should be used as an indication only!!!
We think this is a good test but have not seen enough bars to say for sure

Take an empty coin tube (the smaller the better) and make sure the lid is tight. Stand the tube on the lid. Balance the bar on top of the tube then strike the bar with a hard object. We have found that hard wood works best and does not dent or damage the bar. The bar should ring. The bad bars thud.

You will need a good ear because some of the Englehard bars do not ring as well as others, but when you hear the bad ones thud you will understand....Some bars ring like a bell. Some sort of ring and the bad ones thud. Also all the bad bars have had the same pattern on the ends.

The pattern is a circular pattern that goes from the top (logo side) to the bottom of the bar.
A similar GOOD pattern goes from one corner to the opposite corner.
Please make note: These are indications only and should be used as such. The only 100% way is to cut the bars in two or ultrasonic test them.
.........................................................................................................

The above is the word for word description that was disseminated on the CoinNet trading network and is the product of a Texas coin dealer who posted it. My only reason for calling attention is for educational purposes only. This was a long time ago and I never got any bad bars so do not know if it is correct or not. The only changes I made were in spelling. As I recall, this information was before Englehard started encasing their bars in plastic. I just don’t remember the date except that it was posted on July 24th of whatever year they printed it.

blitzdude

I wouldn't use the Sigma as the gospel. Many fake plated coins pass as real so no doubt it can have difficulties with ones that are legit.