As a 19th century civilian re-enactor, I recently got interested in collecting stick pins to use with my tie as well as to collect. I purchased the only book that is currently available on the topic "Collecting Antique Stickpins: Identification & Value Guide" by the Kerins. It is more of a picture book than a reference book. It doesn't explain how to identify the age of a stick pin.
It basically shows examples from the author's collection grouped according to subject matter (ex. cameos, advertising, horse shoes, type of stones used, reptiles, animals, etc.) As far as I can tell, the subjects of the pins seem to be the same through the use/history of stick pins.
So, are there shape designs that changed through the years? Was the way that the subject of the pin is attached to the actual sharp pin a way to determine age by looking how it is attached in the back?
What makes one pin priced at $25 and another pin priced at $200? Any information would be appreciated. Those stick pins that I've purchased have come from on-line auctions sites and not from being able to examine in person.