Seamaster Strap

Never heard of a “lug alteration” on later models where a standard, straight end 20mm strap won’t fit. Now, if you are talking about fitted straps to match the case, then yes, there are substantial differences.

Also note that most of those straps sold on Etsy are fakes, so not the best quality. There are plenty of high-quality rubber straps out there to buy, but most won’t be fitted, just straight ends. I’m a fan of Tropic straps (the real, Tropic-branded ones, not the “tropic”-like) or the new Artem rubber straps.

If you want a fitted straps, yes, you will need to buy an Omega one AND make sure you get one that fits that case. The ones they sell online are for the modern case and will not fit.

But if you do t want fitted (I.e. just a standard straight-end strap) any 20mm will fit

Normally, I’d not reply because you don’t seem to be understanding what I am saying. But, I took a look and:

1) that won’t fit the case of the older Seamaster you have
2) it isn’t a real Omega strap, but either aftermarket or fake.

Seriously, instead of wasting your money on these cheap EBay straps that put Omega in the title to fool naive buyers, just buy a quality rubber strap from a reputable dealer (like the ones I listed) or go to an Omega dealer and ask them to order a real one that will fit your case.

Otherwise, you are likely to spend the same amount or more on cheaply made straps that don’t work.

Advice given. I’m out of here.