Absolutely no clue about its value, other than the fact that it will at least double with an appropriate (or close) saddle on it... One of those double sprung leather ones should do the trick (and sometimes you can find them in the $15 range in usable condition.)
Because of the historic value of the bike, you might want to go a different route other than CL to try to reach interested people. I am not sure about historic bike clubs in philly, but I suspect there is something of that sort; ask to see whether they have a newsletter or whether you can leave a couple of flyers with your bike (good old bulletin board style...)
good luck, this looks really interesting.