t That is COOL as all get out, man,,,way back when i was a wee lad, i owned a trade dollar that opened up and there was a picture inside.....i wish i had kept her, but needed money and sold it for about 75.00 back then....wish i still had it though (sigh)
I saw a coin something like that on an episode of Pawn Stars. It also had a vintage photo inside of it.
As for why, the craftsperson sold it for more than the coin was worth plus got to keep the sliver from the interior.
check out this one, currently up for auction with Mcvanderstein... https://www.ebay.com/itm/1893-CHRIS...792035?hash=item5485e777a3:g:W58AAOSww2he6W-G