Difference between kowa 664/664ed/664m?

[Djaworow]

What are the main difference between these 3 spotters? 664, 664ed, and 664m…?

Looking to build / buy a big eyes setup and am seeing all of these used but couldn’t find the main differences?

 

[Djaworow]

Ttt

 

[4th_point]

See screenshot. Just note that the 664 has been discontinued. So that sheet is now outdated.

I think that the M designation signified a change to the plastic body material. There might have been updates to coatings as well but I don't know for sure.

I have seen some of the ED marked scopes as well but I don't know where they fit in. They seem pretty old though.

Good luck!