There was/is two different numbering systems on Spyderco blades. Some of the older "upper-end" Spydies had a serial number. They stopped doing that some years ago. I've seen serial numbers above 500. I've always assumed the whole production run would have been serial numbered. A normal production run is often 1200 pieces.
Still continuing is the Collector club. 200 knives of the first production run are engraved for the collector's club. In the collector's club, a person can be a "new model" collector (receives only new models released), or an "all variant collector" (receives every variant of every new model released...so every color and steel of every model). A member of a collector club can choose their dealer. Usually in the collector's club, a collector is supposed to accept ever model they previously agreed upon (obviously until they quit the club), but sometimes a dealer will allow a collector to refuse a model and the dealer will sell that numbered model to someone else. Sometimes a dealer will have one the collector club #'s and sell those off too. Of course a collector can sell of parts of his collection as well.
It is debatable if a collector club # will make a knife more valuable.