If you do not know the service history of the watch and you want it as a keeper, then it should be serviced. Ludmil in Bulgaria is an excellent choice!
Yes, you can get impressive results. I polish crystals on all the vintage watches I buy - even ones that don't appear to have issues. On the best kept vintage watch there will be some microscopic abrasions that a polish will remove and give a new clarity to the crystal.I polished the crystal with Polywatch tonight. Results were quite impressive. Though I didn't do a good job on the rounded edges, as I was afraid of polishing away the plate finish. I think I'll tape off the case this weekend and give it another go on the edges.
Not actually a step-by-step, just a description of what I did. I use microfiber cloths for both applying the polish and buffing it off. If all I am doing is a mild cleaning with the Plastx, I just use firm circular motions on the crystal with the cloth then wipe off the polish to get a look. Repeat as often as needed until you get the desired results. If I am doing more serious case and crystal polishing, I use a 2" cotton buffer ball on my drill press, slow speed, and go over the case and crystal with Maguiars Aluminum & Mag polish numerous times until the desired results are achieved. I then follow up with a hand polish using Plastx. I have never used the buffer ball on a GP case, just hand polishing with Plastx.Oliverb, have you or anyone here ever typed up a step by step instructions as to how you prepare the watch prior to polishing, and the steps you use with the polish? I'll have to search later and check, I think I recall you may have already. I need to purchase some of that stuff and check it out.