My first prewar purchase was a T206 Krause Portrait with an AB 350 back.
I had done a few months worth of research on the T206 set, and I was in the process of selling off my near complete graded 1953 Topps set. I had done my research, set up my spreadsheet in Excel, and was watching what was listed regularly on ebay. The Krause was part of a large assortment of cards offered all ending around the same time. Something about his portrait stuck out to me, and I knew I wanted my first purchase to be an off back, because I knew the backs would be something I would be focusing on with my T206 collecting project(s)
No regrets. I had almost a complete Krause portrait back run assembled before I shifted my collecting goals in the last 6 months, but I kept the AB350 back, and always will, since it is my first. It was originally in an SGC 4 holder (though it was probably overgraded) and has since been snapped out and put in my binder
