Recently I've bought an used JTV-59, which arrived without any allen wrench. Needing to make the usual guitar setup, when I tried with my normal (here in EU) metric allen wrenches I found none fitted in. So I have bought on Amazon an inch size allen set and found that the correct wrench size to adjust the action is 7/64" and the one to adjust the strings intonation is 3/32". I hope this can be useful to other Europeans with the same problem