That is one hellofa modified 290 for sure! Actually it is not a 290 at all. Its a 250 (or a 210 or 230, the Stihl 1123 line of saws).
Identifiable features are:
1) The air filter. The 290 has a clamshell air filter and it sets in place with screws. That is a typical snap-on 1123 air filter.
2) The side cover is a C type easy adjustible one. The 290 does not have that option; its is an option on the 1123 saws.
3) The muffler is a 2 bolt 1123 type. The 290 has a 3-bolt muffler with a different cover plate.
Custom/odd features:
The decompression release. Not stock on a 290 or a 250, but my 250 workshop manual shows a decomp button in that place, so it was obviously an option.
The gas primer. Oddly it looks like the top cover was designed with that on it. So maybe that was an option as well. I have never seen an 1123 saw with either that or a decomp button though.
The shark gills on the muffler look like they have been opened up (modified).
Looks like it has a .325 bar on it, from all the paint being worn off. Typical.
Maybe its one of those oddball Euro models though? They made a weird 230 model as I recall, the L model I think it was? It had a restricted muffler and ran really quiet, but it was said to be a dog becasue of all the restrictions.
