Seller knows the maker of the seatpost, but not the frame? Seems odd.
I realize that that's a pic pulled from a craig's ad, so you haven't seen the bike and can't show us add'l pics, but unfortunately, that pic doesn't show many details (eg, dropouts, headtube junction) that could indicate the manufacturer of the frame. The build seems to be a hodge-podge of different stuff from different time periods, so I'm guessing little(if any) of it is original. Based on that pic, it looks like a typical 24" mid-school race cruiser frame, built up with some nice components from someone's box of spares.. Judging value is tough, at this point.
If you go see it or get add'l pics/info, update on here... maybe one of us will be able to tell you more.... or maybe someone will recognize it immediately..?