I bought a small hoard of 44 pieces of French Indo-China 20 centimes coins at a yard sale recently. They range from 1900-1928. I thought I hit the jackpot with a combined listed value of over $15,000. It turns out all but two of them, the dates have been altered. The last two digits didn't look right. They're off-kilter very slightly. Up until 1921, they were struck on 83.5% silver planchets, the ones I have are on 68% silver planchets (68% was used starting in 1921). It seems they used real coins of later dates and changed the dates to make them more valuable. Here's one from 1915. Notice the 15 is crude and tilted. Also, they never produced coins in 1915. I also have some 1904's and 1906's, other years that don't exist. Here's one from 1912. Notice the 12 isn't consistent with the 19. The last image is a real one from 1928. Notice all the numbers are consistent.
I think this has come up before. They used a common early date and then extrapolated the rest, such as last two digits of the date and silver purity. Also that 1928 looks fake as well
