'Zactly. Some you can figure out without resto, like the Type 1s. Always look for the 16/16. And there is a way to spot 1914 and 1921 from the detail on the braid.
Soak them in ordinary white vinegar overnight. You'll have a partial in one or two nights. Sometimes a little longer is necessary, but if after four or five days, nothing, you're done, that's as good as you can do.
there is a product called nic-a date, but once done, it is an altered coin, some rare dates like the 1918/7 are still worth from 1/8 to 1/2 of ag/g price as a hole filler (rare coins not purchasable in collectors price range, so they settle for damaged/holed coins) i have sold some s- mint ones that would of been about 8.00 in good condition for 2.00 ea at a coins how i just visited as a vendor also, there was a vendor there offering 7 cents each for non dated nickels..