I’ve been looking around a lot at these in the last two years since I started collecting MPs. What is below are my own observations.
Version 1 has the shallow checkered grip. The text on the barrel is FABER-CASTELL . TK-fine . 970x . GERMANY
There is no text on the clip.
Version 1a is the same but with the lead hardness ring pinned in a single position, unmovable. Both can be seen in the photos with dark wood background posted by Patrick above, those are in my collection, posted on Reddit a while ago.
Version 2 has the deeper circular grooves on the grip, the text on the barrel is 0,5 (or 3,7,9) FABER-CASTELL . TK-fine . 970x The word GERMANY is moved on the clip ring.
Version 2a has a bunch of color coded lines on the back of the barrel: yellow for 0,3, brown for 0,5, blue for 0,7 and orange for 0,9.
On both version 1 and 2 the cone has no grooves for 0,3, one for 0,5, two for 0,7 and 3 for 0,9.
Version 3, with the longitudinal grooves on the grip I dont know much about, for example the cone looks different, the color of the grip is off, dont know if its metal or plastic. Would appreciate any additional info on it.
Version 2/2a are the most numerous and easy to find, followed by 1/1a with version 3 the scarcest.
As far as lead size, I’d say 80% of those for sale online are 0,5, followed by 0,3 and 0,7 in roughly equal numbers. 0,9 is by far the rarest.
It had a companion, the cheaper 971x series, with plastic longitudinal grooves on the grip and fixed lead sleeve instead of semi-retractable like on 970x.
