Stumbled onto this article through one of the trivia sites I follow. "Yesterday the Madison Coin Club circulated an article from CoinWeek explaining that mint marks can be added from the inside of the coin." From https://coinweek.com/counterfeits/c...d-mintmarks/
Quote: What's an embossed mintmark? It's a mintmark that has pushed up from inside the coin - that's the embossing process. But how's something like this done? By drilling a tiny hole through the edge of the coin under the place where the mintmark will be situated on the coin. To emboss the mintmark, a device resembling needle-nosed pliers is used; on the inside of one jaw is the mintmark, and on the inside of the other is padding to prevent scratches and other damage on the surface receiving the embossed mintmark. With the mintmark-side of the pliers in the drilled-out hole, pressure is then applied on the pliers and the mintmark is embossed onto the coin from within. The access hole on the edge of the coin is then filled with a material such as lead and sanded or sculpted to resemble the surrounding authentic edge.
Working on: Indian quarter eagles, Chinese pandas, and San Francisco tokens; upgrading my Peace dollar and US Type sets
"Fear is the enemy of will. Will is what makes you take action; fear is what stops you, and makes you weak." -- Sinestro to (my avatar) Hal Jordan, "Green Lantern" (2011)