Sorry, never have sold, (I do not sell anything), but related to platinum the loss of the diesel catalytic market has led to a lower, much less traded, market than the past. 30 years ago it was not common but more available, (and bought), at shows than today. It always has had wider buy/sell spreads than gold, something even more severe today from what I see.
There are still many other uses for platinum especially in things like jewelry and the automotive industry with has stabilized against the electric vehicle.
I still like the metal, and buy Proof platinum eagles when I find them at reasonable premiums. I think its underrated for its rarity, but multiple markets only value gold, which I believe is overpriced versus its rarity.
I have a small amount, I have two 1/10's and a 1/2 oz but I'm not crazy about platinum and once I can make a profit it's sold. Platinum is not gold, gold has pizzaz, platinum has no personality, that's the way I see it!