I believe the MD is the Roman numeral I'm not sure about DAM. Notice the error on the MD right leg? Anyone ever see this?
No to chopmark or merchants mark.. It's an etching known as a Love Token MD are a persons initials @lordmarcovan can maybe tell you more about it I believe that is Chinese and not a Japanese coin (looks like I'm wrong)
That is indeed a Western love token engraved on a Japanese host coin. The creator was likely American, but possibly British or Western European. It is done in the classic late Victorian (ca. 1870s-1890s) style. The monogram was the initials of the person who owned it. It's a neat piece. The engraving is competent but not exceptional, and the unusual host coin is a plus.
I believe that I have "merchant marks" on some Japanese 2-Sen coins. They are countermarked with arabic numeral "2" on the reverse side. What does anybody know about "merchant marks" on coins?
That's unfortunately too broad a question, like "what does one know about books?" or "tell me about cars". There are too many categories and variables. There are references on counterstamps. Brunk is a big one, though I personally have no experience with it. And there might indeed be reference material on Japanese counterstamps like you seek, but that's getting into pretty esoteric territory and maybe outside the scope of English-language reference material. Perhaps @Stork, who collects Japanese coins, will know a little about this, but counterstamps and chopmarks and such can be a pretty deep rabbit hole to go down. I suspect you yourself, @mlov43, likely know a lot more about Asian ad Far Eastern coins than I do. In any event, the coin in the OP does not have any kind of merchant marks or counterstamps. Just hand-engraved love token art. And that at least is a topic I have some familiarity with.
You got to realize that this 10 sen coin is somewhat a tiny coin to work with. I believe it's roughly the size of a dime.
The round silver (gin) counterstamp was used to designate a one yen coin to be used as a trade coin outside if Japan. "gin" mark on the left is Osaka mint, on the right is Tokyo mint. Chop marks were punched by Chinese merchants to test the coin for fakes. They had to be deep enough pierce the surface to see underlying silver