The panel is red backed and has cards 76-80 in row 1 and 85-81 (reverse order) on row 2. It was in a 2017 REA auction and I only found it by chance. The theory has always been 1st series Topps cards were contained in #1-80, but maybe that only applied to black backs?
I recently blogged about this, hoping to find out more but nothing else has come to light.
http://www.thetoppsarchives.com/2023...-is-going.html
Anyone have thoughts on this? I've run it by a few folks with deep knowledge of the 52's and it's a real stumper.