Follow-Up...
1967laughlin#17NOGRADE2.jpg
It turns out the card that they would not grade was one of my
1967 Laughlin World Series #17 submissions. If you're familiar with the set, you may know that early in the run Mr. Laughlin pasted two print sheets of the cards together to 'thicken' them before cutting everything into individual cards.
(He seemingly soon started using thicker stock.)
My guess is the card in question must have been stored in a screw-down holder or something for a long while, because it was so flattened down that there was nothing to indicate it was two separate cards adhered together when I submitted it. However, freed from whatever constraints held it, the last remnants of mucilage faltered and the two cards began to
(now obviously) separate...perhaps coaxed a little by the graders?
Although still somewhat attached, the separation is now clear as day...
1967laughlin#17separated2.jpg