As much as I hate to say it, these are very costly projects. But, on the other hand, done well, they provide the feel/function of any other gen 62xx Daytonas @ a fraction of the price (even if that fraction is still a hefty sum to a civilian).
Oh & sorry about the hard-ons. Try wearing baggy trousers & it will be our little secret.
1stly, with scam-style pics (small & dark) & only 16 previous sales (his only previous visible sale, a Daytona dial, which is itself questionable), you should assume this to be an aftermarket part until/unless he can prove otherwise (with a concrete provenance).
2nd, after a bit of image-editing to unhide some of the details, I am still not clear whether it is a poorly printed gen or poorly printed aftermarket part (my gut says the former, but we are not on speaking terms right now ).
3rd, what you describe as a 'nick' is pretty serious damage & I also see some 'nicks' around the 60.
If you want to gamble on it being a damaged gen, then its value is up to you, the buyer. Without much better pics, I would probably keep my powder dry & wait for the next 1.