I collect manufacturers' sample chips, particularly the ones with the mfgr's name on them. They are historically useful in identifying a specific manufacturer (or distributor) with a certain chip mold. They may also have the mfgr's address, phone number, salesman's name, etc. which can be useful in identifying chip molds. Older molds, such as C&J are particularly interesting, but even newer samples are fun to have.

The B&G sample plaque you show is collectible and probably worth $15 to $30 on the collector market to the right individual. One thing to keep in mind is the size of sample plaques (usually measured in mm) which are typically smaller than "full size" plaques you may have seen. For reference, the sample plaque you show is probably about 1 1/2 times the size of a business card, whereas "full size" plaques like the Sahara $100 plaque is considerably larger.

I don't know of any book or price guide on manufacturer samples. You will find some mfg. sample chips in Gaming Archaeology's auction catalogs from time to time. See also the color covers of the last CC>CC quarterly magazine for reproduction of some B&G catalog illustrations.