No, don't have time right now to fabricate a piston stop. I'm operating on the assumption that it has. Do they generally slip towards retarding the marks? I.E. making it look like the timing is much more retarded than it actually is?
Without standin in front of one, I'm terrible at guessing. So I'm just not sure. It should be fairly easy to see. If the rubber ring is all distorted and twisted looking, then chances are pretty good.