There’s also loads of info on Garvin’s excellent Vintage Airguns Gallery, here, the other place, etc. It just takes time to find it and absorb it.

And lots of good advice (apart from mine, though the book is really good) in this thread.

In looking for any collectible, there’s always a big risk of buying the first halfway-decent one you come across, and only later realising that it has flaws or other issues and might have been not the best value.

While Mk2s aren’t hard to find, many have been refinished/“restored”, or are bitsas, and there are some non-original parts around (eg repro barrels in .25”), and plenty of people who are either chancers or honestly overrate what they have and ask spendy money for average items.

You are doing the right thing in your research. As my military friends say, time spent in reconnaissance is never wasted.