FBP was a gasket mounted separate safety glass? Would that glass and gasket generally come with the new CRT?
I suppose a small catch of those would create quite a frenzy if they get listed on ebay, but it all depends on how many there are. One at a time always works to the sellers advantage. For reference - a few b&w 21" NOS RCA recently sold for $100-150 each, plus most buyers paid a hefty shipping fee.
I'm guessing a known good NOS color roundy CRT could bring $300-500 at auction.