Congradulations on your new find. I love when someone doesn't know they found a new variety and I can be the first to tell them. Makes me happy
Like @Michael K said it seems like this would be more desirable since proofs are usually inspected, and in turn, with a die crack, more scarce. Personally I steer clear of proofs below PF70, unless it's obtained at FV, but I think I'd pay a premium for this one, even if it came in at PF65, just because it's a proof with a nice error. And I'm not even an error hunter. Very nice find!
Not all proof errors are spotted by the Mint even though each coin is hand-processed. I found both of these 2005-S KS silver proof "goofs" in separate SQ holders that came from the Mint in the same order. Chris