I would think if its in good working condition, well worth $100. If you need a saw to run a 20" to 24" bar I'd buy it. Heavy per cc by todays standards but blocking up big wood, your not toting it that much anyway.
Well, I bought a 10-10S for $50, with 20". Heck of a good saw for the money. I would hesitate to drop a c note also, I mean I hesitated to drop a 50, but the bottom line is you probably won't regret it.
What else can you get for the $$, for example a 28" bar & chain kit costs about $100 new.