ps
in the "old" Stihl numbering scheme, if the last digit is EVEN it's a "professional use" saw with jug-on-cases engine construction: 024, 026, 036, 038, 046, etc
in the "old" Stihl numbering scheme, if the last digit is ODD it's an "occasional use" saw with clamshell engine construction: 021, 023, 025, 029, 031, etc
in the "new" Stihl numbering scheme, if the middle digit is EVEN it's a "professional use" saw with jug-on-cases engine construction: MS240, MS260, MS360, MS460, etc
in the "new" Stihl numbering scheme, if the middle digit is ODD it's an "occasional use" saw with clamshell engine construction: MS210, MS230, MS250, MS290, MS310, etc
basically, old 025 = new MS250, old 026 = new MS260, and so on.
AND
in the new scheme, the last digit is the "iteration/version" of the saw.
for example
MS360 first version
MS361 second version
MS362 third version (current production)
AND
the letters after the model designation indicate a specific feature on that version
for example
MS362CM has (M) STIHL M-Tronic system
BUT
there are at least three exceptions to the naming rules i posted above, where it appears that the Stihl product naming people went off the rails.
- MS180 (current)
- MS280 (discontinued) (this was one of the first "intellicarb" models)
- the many incarnations of top handle saws.
there may be others.
my family closed our building supplies store in 2004, so i have not been a Stihl dealer (all of which are 'servicing dealers') since then, hence there are probably some additional model naming outliers.
please don't ask me to explain the Stihl numbering scheme further.