There are many experts in their fields that are experts because they have those catalogues and can positively identify items. Silver dealers have always scoured markets looking for those that Gorham, Durgin, Edwards, and all the other manufacturers put out to inform their retailers what was available. There was even a ten thousand dollar reward out for an original Belter furniture catalogue. Even old bill heads and magazine ads can identify a pattern or design. Glass, china and pottery collectors and dealers are just beginning to become aware of the fact that there are paper pieces that can help them identify items - and often are nice decorative objects in their own right that they can frame or place beside it to advertise and identify the piece.
Earlier cards are lovely and some even come as tobacco silks.
It is some of the later period that we know less about, because many of these companies were small, regional companies or didn't last too long. Every now and then these companies mailed out post cards or inserted cards with price lists on them which are a micro- wealth of information. From this small piece of paper we learn that it is flameproof and would be replace for free if they broke. We learn that Informal was a design by Ben Seibel and what pieces were made and their cost. This was probably in the late '50s or '60s.