Ok from what I found on the interweb leads me to belive this is a 55-56 Fomoco convertible rear arm rest... how much should I ask for it? The only one I found was a nos one on ebay and they wanted $400...there have been no sold ones...
I bought a pretty ****py one for my 46 Olds, $10.00 as I only wanted it for the folding mechanism being that car will be eventually retrimmed. Freight here cost me more than armrest did. Then not so long ago I located a freebee from a local wreck. The market will dictate sale price. Throw it out there and you might be surprised. If it doesn't sell it won't take up much room when stored. Supplies of these hard to get parts are drying up and someone will want it at some time.
From the single picture looks like its from a 55/56 Ford but the Crown Vic' was the only model with a folding armrest. Pretty limited market regarding stock replacement, if the folding mechanism is in good shape plus tight then maybe in the $50-$100 range. For what it is worth a whole back seat is currently on eBay for $200 with no bids.