How can he tell people they were dropped in vinegar in 1941 if one of the coins is from 1944?
Well, just don't eat the coin if you're worried about lead and/or arsenic.
I'm no expert. I can't find any coins on the internet that aren't labeled fake with 10,000 yen. All the coins have yen values much much lower....
From google search of ten thousand yen coin: Ten Thousand Yen, The Twin Dragons, Meiji 8, Silver 900, Dia 88 mm, Thickness 5 mm, Weight 180 gr....
Just tell people they were dropped in vinegar in 1944 accidentally after news of the Germans bombing Pearl Harbor reached the owner.
Separate names with a comma.