Advice for a replacement crystal for a Speedmaster Mark 4.5

Hi all. I'm looking to replace the very scratched crystal on my Omega Speedmaster Mark 4.5 (reference 176.0012). These come together with the tachymeter bezel.

Found this seller on eBay that sells them new for a very decent price, claims they are genuine Omega, and has a reputable store with plenty of good feedback. Comparing the not that great photos in the listing with the tachymeter on my own watch seems like they match. It does seem a bit too good to be true though, as these should sell for more than that.

Anyone with experience can tell if these are proper genuine Omega crystals?

FWIW Seller is member here and is a watchmaker so I would guess genuine

I know nothing of the MK4.5 but the crystal for the MKII is a bear to self install. (If you don’t have a specific tool for that crystal) Google first to make sure you can do the install if you haven’t already.