Edge Lettering

Philip

Can somebody point me to a website outlining the process of minting coins with edge lettering?

A couple of days ago a friend of mine asked me how edge lettering is minted on a coin and I was unable to answer My confusion stems from the fact that the obverse and reverse of a coin are minted by applying "vertical" pressure on a planchet, whereas for the edge lettering the force is "horizontal".

Conder101

There are two ways of applying lettering to the edge of the coin. The first one is through the use of a castaining machine. In this device there are two flat edge dies, one fixed, one movable and each bearing one half of the edge inscription. The fixed die is fastened to a tabletop and the movable one is set so that as it slides past the fixed die the distance between them is slightly less than the diameter of the coin. The planchet lays flat on the tabletop and is squeezed between the two dies as the slide past each other. This forces the letters on the edge die into the edge of the planchet. (The planchet will turn a half revolution during this pass. If the dies are not retracted all the way before the planchet is placed between them you can have missing letters on the edge or an overlapping of the inscriptions.) This can be done either before or after the coin is struck, but if it is done after there can be warping of the coin and the work hardening of the metal will wear the edge dies out faster and the impression of the letters into the edge will be weaker. If it is done before then a close collar either can't be used or it must be a reeded collar. A close plain collar will crush the edge of the coin as it expands and flatten out the letters and wipe them out. The current British pound coins are made using the letter before striking and then strike in a close reeded collar. this allows the lettering to remain visible.

The second method is through the use of a segmented collar. The lettering is on the inside of the collar but the collar is made up of three or more pieces that come together, the planchet is dropped in and struck by the die then the dies and the collar pieces retract allowing the coin to be ejected. As the coins are struck the metal expands outward and is forced against the letters in the collar. (Die vertical force causes the coin metal to apply a horizontal force against the collar.) The US Saint-Gaudens gold coins were struck using the segmented collar method.

Philip

Thank you for the detailed explanation

laurentyvan

I have always found Conder101's posts to be full of expert, knowledgeable detail-one of only a very few who post at this level across the breadth of the numismatic landscape..

Edge lettering can be fascinating and I have a better understanding of the process-thanks!