Going through my too-large collection of dice I saw I had two GenCon promotional dice (and nothing else of possible value except some Middle Earth CCG Eye of Sauron dice).

One is the red d6 from GenCon/Origins 92, which has a recent eBay sale for $20. The other doesn't actually mention GenCon but it has the 1990s TSR logo in place of the 1 and I don't know where I would have gotten it except GenCon (1993 or 1995-9 - haven't been since then). It's marbled green and large - 3.5 cm on a side. Any value?