Right you are, Bill...and that supplement went on to become O Scale Railroading Magazine, purchased by Myron Biggars after Vane Jones death. Sometime, it morphed into O Gauge Railroading, but I don't remember whether that was before or after it was acquired by the present ownership and brought to it's present prominence in Model Railroad publications.
I was a subscriber to Traction and Models early on, and have bound copies of the entire run in my library. Since I was a subscriber when the O Scale supplement began would that qualify me as a charter subscriber to O Gauge Railroading?
By the way, I can attest to the fact that the first regular edition of Traction and Models bears a March, 1965 cover date. An eight page prospectus edition dated June, 1964 was published and distributed free at train shows, hobby shops and by mail to those requesting it.
