Burdick unquestionably stamped cards. I saw some of them at the Met when I was researching my book. That is how I first realized a card I had was a former Burdick-owned piece: I recognized the stamp.
If stamping a card blows your mind think of this: Burdick
pasted down every card he donated to the Met.
Has anyone had any success at getting a TPG to acknowledge the provenance on a holder?