Striking 39mm gold medals - Double Split Gold Piedfort
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When looking over the information for the Gold Trump Dollar from Bernard von NotHaus, he lists the challenges in making a UHR gold medal the size of a silver dollar which led him to create the Double Split Gold Piedfort which uses 3 planchets and consists of 1 ounce of gold and 1 ounce of silver. I was wondering if others with experience and knowledge striking gold medals of this size could comment on challenges of striking gold medals of this diameter. I know Dan regularly makes larger gold medals and would love to hear his comments.
Here are comments from Bernard with an edge photo.
The Double Split Gold Piedfort Story*
By Bernard von NotHaus – Monetary Architect
The problem with minting a 39mm one ounce .9999 fine Gold Proof is that as gold is denser than silver or copper, the most expensive specimen in a three coin gold set, is always smaller. That problem has always been an eyesore for me. I always wanted all three specimens to be the same size and have the same quality. Technically, the problem is that a one ounce gold planchet is soo thin it limits the relief of the gold die to being very shallow and eliminates using an Ultra High Relief (UHR) die completely. So while the UHR die works for the silver and copper, it does not work for the Gold Proof.
The solution to this mint dilemma was to invent a new mintable item. Based on my two previous piedforts: the 39mm two ounce silver Liberty Dollar Piedfort in 2004 and the two piece quarter ounce Liberty Dollar Split Piedfort in 2006, I invented the 2016 Gold Proof Double Split Piedfort for the Trump Dollar Gold Proof Set.
The Gold Proof Double Split Piedfort is a unique coin structure with three planches: half ounce .9999 fine gold planchet on the bottom, gold clad one ounce .999 silver planchet in the center and a half ounce .9999 fine gold planchet on top. All three planchets are minted at the same time with an UHR obverse die and voila – a stunningly Gold Proof Double Split Piedfort is created so the Gold Proof Set has three proofs in gold, silver and copper that are all the same size and all struck with the same UHR obverse die.
The 2016 Trump Dollar – Gold Proof Double Split Piedfort Set – consists of one ounce of .9999 fine gold, two ounces of .999 fine silver and one AV ounce of pure copper. It was engineered to be the best, most innovative and most unique, commemorative coin set for an equally innovative and unique Presidential Candidate – Donald J. Trump.
* Piedforts are an old European tradition, dating from the late 13th century in Bohemia. According to recent "encyclopedic dictionaries" by Richard Doty and R. Scott Carlson, other early minters of these special productions included France, Germany and England.
A Piedfort, French for "strong foot," is a special minted coin or medal on an unusually thick planchet, usually twice the thickness of the normal issue. Different reasons for piedforts have been advanced with the most accepted reason being to show examples of an engraver's work or to provide added thickness for striking ultra high relief coins.
France started producing modern day piedforts of its circulating coins in 1967 and continued such offerings regularly through the 1970s. In the 1980s, Carlson notes, there was an upsurge in popularity of piedforts among collectors. France offered piedforts of the silver 100-franc commemorative for the 100th anniversary of the Statue of Liberty.
In addition to piedforts being double thick, “split piedforts” have been minted with two planchets and on special occasions piedforts have been minted in precious metals rather than the base metal of circulating coinage. In addition to European countries, US Mint has shown no reluctance to mint its own piedforts with variously packaged sets, reverse proof coins and other exotic numismatic issues to the cheers of many collectors.
Comments
Very interesting... would love to hear more about this. I know nothing about coin striking - well, other than what I have learned over the years from forums and books....never actually any practical experience. I wonder how much molecular bonding takes place? A cross section would be interesting... Cheers, RickO
Contrary to general opinion, gold is one of the trickier elements to strike.
It is soft and malleable and bends easily. But it doesn't really fill the dies when struck all that well. Of course, increasing the striking force can get a complete fill of the dies, but doing so also can often result in "finning", where a thin wire ridge of metal is squeezed out between the collar and die. This "finning" is often lopsided, being more severe in some areas and less severe in others.
A typical 1-troy-oz silver round is 39mm in diameter. I've done a number of coin club medals where some 39mm copper, silver, and gold medals are desired, but the club doesn't want the expense of making smaller 34mm diameter dies just for a few 1-troy-oz gold pieces. Since gold is right at 60% denser than silver, a 39mm gold blank of the same thickness as a 1-troy-oz silver blank would weigh 1.6-troy-oz (almost exactly 50 grams). So I commonly mint 39mm gold pieces with a 50 gram weight. That way, a coin club can have copper, silver, and gold medals where all are the same diameter and thickness, and all are struck from the same die pair.
The thicker the planchet is, the easier it is to get a full strike with high relief, so long as it is struck in a collar. Broad-striking a very thick planchet can result in a lot of radial deformation and not necessarily a complete die fill.
So, as long as the collar is deep enough to handle a very thick planchet, and the coin press ejection mechanism has sufficient travel to be able to fully eject a thick piece from the collar, there will generally be no problems.
It appears that the medal described in the original post of this thread is basically an unbounded layered planchet. I would think that the medal layers would easily separate if taken out of the holder. That might actually be desirable in a situation where the medal was to be melted for the precious metal content. So, essentially, it would be easy to separate the 999 gold from the silver.
Good post!
Nice post Dan. I did remember that the 39mm gold medals you struck are 50g gold.
It is interesting that the Shanghai Mint is able to create medals that are 31.104g .999 gold with a 40mm diameter, such as the 2016 ANA Anaheim medal. I wonder how they do it.
They did a pretty nice job on that ANA medal.
The relief is actually quite low on that one, and so that is how they were able to do it. The only significant relief is within the inner circles (far from the rim). The California half dollar icon is about 44% of actual size (13.3mm diameter) on the medal. The relief height on that icon was also apparently scaled down by a similar amount (about 44% of original), making it fairly low relief. The two bears are quite low relief, but the right frosting and polishing of the die helps accentuate the shallow details.
cool thread, thank you
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Are US Mint reverse proofs piedforts? How many peidforts has the US Mint made?
That's interesting and worth asking Bernard about.
If the layers could be separated after striking, would be interesting to see what the center layer looks like...
Michael Kittle Rare Coins --- 1908-S Indian Head Cent Grading Set --- No. 1 1909 Mint Set --- Kittlecoins on Facebook --- Long Beach Table 448
The club medals in 50g gold look great too! Really fun to hold a few of them in hand as they are so much heavier than the copper and silver pieces. Here's a pic of our 2014 Glendale Coin Club medals in copper, silver and gold that were done by Dan, all 39mm.
Michael Kittle Rare Coins --- 1908-S Indian Head Cent Grading Set --- No. 1 1909 Mint Set --- Kittlecoins on Facebook --- Long Beach Table 448
I love the Glendale Coin Club medals and it's great that you can make them every year.
You take such nice photos of your coins for sale, I was wondering if you have photo archive like many dealers do? Looking through your archives would be quite the treat.
Here are two of your photos I saved from previous sales.