The version numbers refer to the M-tron control module firmware, not which clutch cover or other production changes are introduced during model feature revisions. The MS261C-M model evolution "versions" shouldn't be confused with which version of M-tron software is in the ECM of a given saw.
That's typically where it will be found on domestic saws according to a tech note I've seen somewhere (along with seeing them there personally). It may be in different locations on different models depending on where the "emissions label" and "material number" is located, though there would be no surprise with Stihl changing locations depending on which way the wind is blowing on a given day.
The M-tron version number being on the sticker began with v2.1 of the software which was the first version to use the calibration procedure vs. the earlier "reset" procedure for initially setting up the saw or otherwise re-establishing optimum operational parameters in the event of performance issues or major component replacement. An M-tron saw without a version number on the sticker is presumed to be pre-v2.1 (pre-v3.0 here) and requires the "reset' procedure vs. the calibration procedure. According to everything I've read, there were never any v2.x M-tron saws distributed here and we went directly from v1.1 to v3.0 firmware. As mentioned, that can probably be debated on the basis of subtle ECM firmware tweaks along the way, but public domestic version numbers in the states do not include v2.x implementations. That is probably irrelevant. LOL
Sure you will. Not common, and not on a new saw these days, but v3.0 firmware coils were available early on as upgrades for v1.0 and v1.1 coils on MS661's that still had black solenoids. I believe that upgrade may have migrated to 441's as well, but have no direct experience there. In other words, the solenoid doesn't determine (or care about) the version of M-tron software on a given saw. Some just work better than others. There were several black solenoid modifications along the way that were applied to any/all of the different versions of M-tron software/firmware in the field including early v3.0 implementations. They simply appear to have finally gotten it right with the white one and the finer pickup bodies. That said, if I had a v3.0 saw with a white solenoid that went south on me and a new black solenoid on the shelf, I'd hafta think long and hard about spendin' 80 bux for another white one until the spare black one went bad too..., even though Stihl claims they're not interchangeable. They are. (I understand their desire for conformity, but I understand my desire for practicality better.) They'll also tell you to replace a black solenoid with another black solenoid (which is known to be inferior to the white solenoids) because they have a million of em sitting on shelves and want to get rid of em at 40 bux a pop.
Sorry for getting so long winded here..., and back to the original point.
If there's no v3.0 designation on the sticker, the gen 1 and gen 2 model 261's are either M-tronic v.1.0 or v.1.1 firmware.
Apples and oranges between model changes and firmware versions.
