If the price is right and you like it, buy it and have fun wearing it. The manufacturer's mark is usually found on the clasp of a necklace, bracelet, or earring clips and on the backs of pins. Sometimes the identification signature is so small that it can only be seen by using a loupe or other magnifier. Frequently, the mark is on a small tag that is soldered to the jewelry. Often, it can be found stamped right into the jewelry, and in some cases is integral to the design.
Condition is a very important consideration.
These pieces are damaged more easily than fine jewelry and they are also more difficult to repair. Replaced rhinestones and some wear are acceptable to most collectors, but re-enameling, replating and soldering often are not. I just want to add a word about caring for your treasures. The greatest threat to rhinestones is water because of the foil backing. If even one drop of water seeps behind a stone, it will tarnish the foil.