Here is the real story on this. The way it happened was he found me. He called me and told me he had a guy coming over to buy the saw and wanted to know if he was good on the price. He told me he had agreed to sell the bar and saw for $210.00 And the guy was going to be there on his lunch brake.
So I was honest with him. I told him the saw could bring about $250 on ebay with a generic bar. And if he separated that bar from this saw he would bring considerably more.
Then he asked me if I wanted to make an offer on it...."no, you asked me for advice, not to bid." Then he asked me what I would do for the guy coming over to buy it..."if I had agreed to a price prior to the guy seeing it, I would stick to it. And there is no way you can back out of this deal without being sleazy."
So he called the buyer up and talked him out of buying the saw, and the buyer agreed. Supposedly the guy was pleasant with the saw owner.
I would suggest that you talk to the guy and tell him I told you to call. Buy the whole thing for $300. clean the saw up and if the bar does not work on your saw, sell your saw and keep the 051, if it suits you. Then sell all your old stuff on eBay to recoup the money.
If I were going to negotiate this deal, I would be getting all bars, chain, and chainsaw related items for the $300. (he has chaps there too.)