One would hope that they retain some records on their previous models. Or at least who has them now, and how to contact. I suppose if you knew where to look, one could delve through Plaubels tax records. . . Interesting that most of the other serials seem to have two letter prefixes, yet mine just the one. Possibly K, H, OB, and OK refer to different markets they were produced for? Single letter for domestic, double for export or vice versa?