But if nobody in the market knows it exists, how can the market decide what it is worth?
Ebay is the largest auction house in the world. Believe me, it will be found by enough people. All you need is two idiots who want it. (Sorry, Blackie, no offense.) If you have three bidders and at least that many auction watchers, you'll get what it's worth.
You could always buy a ticket to Baltimore, spend a grand on hotel rooms and meals, drop a hundred on show admission to the National and walk it around to all 600 tables next month. You'll get low balled so many times you'll have to wear a cup, and end up selling for less than eBay.
You can research it all week and still not know anymore than you know now. You can put a reserve on it and scare away a couple of bidders. You can grade it and it'll come back a 3 or 4 due to the back crease.
Just sell it. It's not like it's Mantle or Ted Wms.