Yeah yeah.
I did preface by saying "to me" (thus implying personal preference) -- and even in my thought, I didn't say it wasn't important to have backpaper, just that it isn't always a deal-breaker (again, for me). Too, and I should've clarified, thats my feeling about pinbacks in general, as opposed to strictly P2s (which are a bit more "card-like").
Yes, Ed and Al are right. Condition definitely matters.
That said, if a raw Large Letter Lajoie or Young came up for auction without paper -- I feel confident in saying the hammer price would be just as competitve (or very negligibly different) than one that had it.
Yes, of course, if you are a high-grade P2 collector, every facet of the pinback matters: face, centering, clarity, backpaper, etc. just a little bit more than a common example. Even if you're not, Ed is right, a P2 is considered "whole" with the paper, and its great to have.
I'm just sayin', in my humblest of opinions, if you asked most pinback collectors, the celluloid's condition/face far outweighs anything that displays on the back, when deciding to pull the trigger on buying a piece.
So, If someone wants to dump their paperless Cobbs, Mattys, and Speakers, give me a call
Al is right, the Duffy is perfect -- congrats on picking up a great piece.