Looking for aqua terra help!!

my first post on here , I own two different seamasters , and am unsure about one of them. I’m looking to replace a metal bracelet with a synthetic or leather one. I guess I’d like to stay omega original , but have no idea how to go about finding the size to get for aftermarket, or how difficult it is to switch one out. Can anyone tell me what exact model this is? Or what size band I need to order to give the lugs the perfect fit?? Any help great appreciated!! Any and all advice sought and needed. Also, what color band do you think would look good with straight silver?

early aqua terra model:
ref:055ST1681110
21 mm band width

Apparently I was told it was the “ large “ model? Is that just in face ? Or bracelet also?

I am not sure of the terminology usage, but I guess it can be correct as that is the largest 3 hand date aqua terra since it is a 42mm

So what width would the band be as far lugs? Any suggestion for aftermarket leather ? Synthetic?

I’m
Measuring 22? For lugs?, but it’s so hard for me to be accurate within 1 mm?