The market for those saws is hit and miss. 090g's are kind of their own thing so folks really want one or definitely "do not".
Somebody correct me if m wrong but, haven't the gear drive 090's been discontinued since the 70's or early 80's.
When I bought my first 090G I inquired with Stihl about any information on the model that may help give me an idea of it's vintage. Part of the response I got from them was this:
"The 090G was produced from 1969-1985. In 1980 we switched from 7 digit serial numbers (like yours has) to 9 digit serial numbers."
One thing I'm not sure about that I would like to know is what year & s/n they switched from the embossed "STIHL" on the shrouds to the metal plate shrouds. I did recently learn from someone very knowledgeable in the 1106/1109 series Stihl saws that the earliest 090G's had chain drives like the Contra G's as they were finishing up with those parts prior to the switch to the true gear drives.