Have a solid gold Seamaster that will soon hit the block, problem is that the hallmarks are to worn to be able to make out the quality. Appreciate that acid testing involves a rub with a stone but how big a rub? enough to leave a permanent mark ? Electronic testers appear a bit expensive for a possible one time use so anyone who has been in this situation what was your course of action ?
A touchstone isn't necessarily going to prove anything, since gold filled or capped will usually show up as positive. The outer layer is karat gold, of course. If the case is too polished to see the external Swiss hallmarks, then a trip to the watchmaker with a camera would settle the question. gatorcpa