I was at a flea market the other day and I was looking through someone's buffalo nickels, so I got ten for ten dollar two had there dates smeared off, but both had D mint marks. When I got home I mixed up some vinegar with hydrogen peroxide and put it where the date was supposed to be, and it showed up 1914. The back of the coin looks amazing, but the front has some of the head and date smeared. Sorry I can't post a picture right now.
There's some trade in "restored" (acid-dated) buffalo nickels. Values are many times lower than a problem-free coin, but higher than unrestored dateless coins. So there's some incentive to soak dateless coins, especially if they have mint marks. Restored 1914-D nickels frequently go for less than $10 on eBay. Here's a link to let you see what they've been selling for recently (sorted cheapest first).
Dilly, on your dateless Buffs, just use the white vinegar. Put about an inch in a glass jar and drop the coin in. Most of them turn up dates and mint marks in a day or a matter of days. Don't just apply the vinegar to an area, as that will leave an outline. The vinegar will impart a smeared-out look, overall, but that's a small sacrifice, given what you're getting, a date. I dated a lot of Buffs, I know. Lol.
