There were well more than 2 models of it.
And you seem more than keep to imply ours were broken... So, I shall repeat, mine was new from the box and wasn't in the process of breaking down. For what it gave me, it was totally reliable. I knew I could always get a certain amount of response from it. I just wanted a higher level of response, eventually. It wasn't in the process of losing an axis or two. All the solder points were good and clean. I opened it up many times. I studied it carefully because I was going to modify it after many years of faithful service. It was in perfect condition.
In fact, I've almost never heard that Sidewinders had a stellar reputation for perfect accuracy. You're the only one I've ever heard make that claim. I *have* heard, over the many years and many forums, that they are decent but not great, and they will never wear down unless you physically break the plastic. That matches my own observations, as I've spelled out in the previous post.