Weight, and complexity as well as factors like efficiency, noise emissions and vibration levels model spec. Design era, which will tell you a bit about performance vs. There are three factors I think you're trying to assess in secondhand saws.

The characteristics of most models change very little throughout the production run - your 038 would still have been heavy and thirsty whether it was built in 1982, 1992 or 2002 - it would still essentially be based on 1970s technology. You can date them from the serial number, but I'm not sure it would help you very much. From what I could find stihl only put date codes in the serial number on. A real beast and workhorse, and bought used about 15 years ago. The first digit is ONLY a country of origin code, not part of the serial number. Stihl 026 year made? Almost impossible on a stihl.