16760 endlinks dilemma: 501 501b?

[wyattearp]

I've read through as many threads on this topic possible and still haven't found a definitive answer. While it seems many people like the 501s on the case, I have a 501 and a 501b on mine (which work on the case but are still tough to affix) with the 501b fitting more accurately.

Here are pictures of the 501 and 501b on the case:

The 501


The 501b


As you can see, the 501 had quite a large gap between the top of the endlink and the bottom of the bezel, while the 501b has a more accurate fit closer up to the bezel. The 501b was also easier to install.

I guess what I'm asking is if there were variations of each endlink made having slight differences, and what watch were the 501bs made for? Because they are both basically the same design, neither one has a 'gap' for a non side holes case tool, as people have said before.