Huh, never heard that. Are Nickels JFCs or JNs (Jefferson Nickels), and Mercury Dimes MDs or WLDs, and Roosevelt Dimes RDs or FDRDs? I know WL Halves and SL Qs.
If you are selling, just go ask dealers if they want to buy. They will let you know what they want to pay. You are under no obligation to accept. If you don't accept or they don't want to buy, ask if they know someone there that might. I got 45 dollars more for one coin because the guy I was first offering it to looked at a sheet and made an offer. It wasn't his specialty and I knew the particular coin should fetch more than that price for me. So I said no. But I asked who he might recommend at the show and he told me of a dealer that personally collected that series. That's where I went to and sold it to him.
My best luck with trading thus far has been going to the dealer with certified coins, a raw coin I want in mind and saying "what's your price on these if I turn around and put the money back in your hand and then some for this other coin in two minutes?"