As for etiquette, I think it's adequate to ask before handling a firearm. I always ask first, or if they're busy, I only roll it over and look at it on the table. Having had my own tables for years, I know what it's like for someone to pick one up, slam the action, and then dry fire it.....

It's hard for a sasquatch to keep his mouth shut.....
As for a Curio and Relics dealer, those serial numbers won't be in the system unless they are reported stolen. If they are fresh imports, such as the latest 1895 Mausers, it's doubtful any are stolen. I'm not sure about up there, but here, if you enter the serial number in the PD database, it only kicks it back if it is actually stolen. Unless the officer writes it down, there is no record of it being ran through NCIC. It dumps that information every 7-24 hours, depending on the system load. Even if it's reported stolen after running the number in an hour, they system won't catch it. It just works on current input data. If it is stolen, and you are willing to turn it over, typically, no charges can be pressed, as you just bought it, or are interested in buying. Laws may be different in NY state, but here, most officers give you the third degree. If you are honest, they can't really do anything about it except take the firearm into custody. I've had that happen a few times with the local County Sherriff. They are always glad to get the firearm back to the owner, as it speaks well of their reputation. I also have a reputation for doing a lot of trading, and knowing who is trying to sell what in the area. If a certain collection has been stolen, I usually see some of them, and know who has most of them..... As of right now, there are few petty thieves in the area... . Seems some got shot a few months back by an old man in his trailer with his shotgun, and there really haven't been any break-ins since.....

I love Texas! Diesel theft is pretty rough, you can't leave a tractor parked off the side of the road anywhere for more than a day or the tanks will be drained!! They hit my neighbor two weeks ago for over 200 gallons... . Not sure where they put it, but that's a lot of diesel!! Even at $. 44 cheaper a gallon, it's still over $3. 50 here.....