Omega Speedmaster Date 3513.50 cal 1152, anyone know where to find parts number schema/list?

Hey all, this is my first post here as I recently acquired this watch and wanted to open it up to inspect the movement. Now I'd like to change the case back gasket, but did tons of searching and nothing conclusive comes up for the usual keywords. The only website I found that pops up for 175.0084 is https://www.ofrei.com/page990.html with OME-G281-272. However, I've seen part numbers like 198ZW5031, 198ZW5029 or 198-0080. I'm assuming there's a more popular ref that's the same as 3513.xx which has the compatible parts list, but haven't found it.

If anyone can share some knowledge, I'd be very thankful!

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Btw– in regards to the overall watch; the main thing I found weird was the freehand writing in the case back, but fell on a thread from here that went into detail on that. Feel free to share any other thoughts if something is off.

Edit: also forgot to mention serial starts with 586, which seems to be the 1998 batch

Thank you Archer! Honoured to see you drop by. Your name has shown up in every thread I’ve been lurking before signing up, so you’re a legendary figure in my eyes now 😂