is this rolex caseback legit?

[larryccf]

i acquired a box of watch parts etc at an estate auction a number of years ago, with this caseback in the box. THere were a lot of rolex items, bracelet clasps & diver's extensions that all proved legit.

But something about this caseback worries me, mainly the engraving on the inside surface just doesn't rolex factory quality to me - i'm not by any means any kind of rolex expert so i figured i'd throw this out there for someone more knowledgeable