Sorry, but I see a genuine cancel here. Philadelphia used abbreviations for itself in cancels, and I believe
this reads PHILADA with the last "A" superscripted, followed by PA. It might be just PHILADA PA. The bottom reads (POST OFF)ICE. Compare with this cover being sold by one of our members. The salient part is also lightly struck, but you can tell by the spacing of POST OFFICE with the rest that it is the same cancel that you have:
Also note that both envelopes are addressed "Philada".
As for the other part, is this what you mean by cracked or scratched plate?:
Hard to tell what this is from here. But if the grayer spots are gouges or abrasions, then it would be just incidental damage and not a plate flaw. Take a look with a good magnifier or blow up your image further.