Lew Horton is a major distributor with enough clout (and credit) to get special run guns produced through regular production as well as the Performance Center. They also distribute catalog guns and you can’t always tell by looking whether they handled a specific gun or not. Their name won’t appear on the gun. Special runs can have unusual barrel lengths, stocks, porting and other non-standard features, but other distributors (RSR, Davidsons, Camfour, Tallo, Ellett Bros …) have commissioned special runs as well. Some guns initially exclusive to LH became available to any distributor.
Some of the more desirable Performance Center guns were Lew Horton exclusives and there seems to be a premium when their name is attached to a gun, so be careful. If you have the original packaging, the product code can help ID a gun.
Buy the Standard Catalog of Smith & Wesson, 3rd edition and start reading. If you like S&Ws, you need a copy.
http://www.amazon.com/Standard-Catalog-Smith-Wesson/dp/...id=1214789769&sr=8-1