I only know about Bill Hurlow and his way of dating a frame. I workd for Condors for 2 years as a boy,but learnt a lot. Bills prerfferred method was your birthdate, plus the date of the year ,so mine was 1010 60. Many fame builders numbering system was based on the DOT and any number youwished> Remember,these wewre frames that bore no history and proninence is only a recent thing. In those days, we could buy an ex pros frame for the same as an ordinary one. Provinence has increased vcalues, and unfortunately,greed and fraud.Barrie Carter Roundham,UK