It's a combination of all of the above, plus TCDB and
https://baseballcardvariationsguideb...wordpress.com/
for the most part. Also these boards.
I think I define 'master' differently than some. I only include variations which result from human error - misspelled words, incorrect layouts, "traded" lines, things like that. So, Washington, Nat'l League and the Cubs that started this thread? Yes. I don't include accidents from the printing process itself - so, no Frank Thomas NNOF, 1967 Spiezios or Schaals, etc. I'd be chasing fish eyes and other detritus forever.