It is easier to date some vintage and antique brooches, compared to other types of vintage jewelry, by inspecting the clasps used. This is because some clasps were used on much older pieces, and the date of introduction of some of the newer clasps is definite.
There are many varieties of clasps used on vintage brooches - C Clasps, Trombone or tube clasps, Safety pin clasps, Early safety clasps, and modified C Clasps.
The C Clasps are the earliest type of clasps used on brooches, although a modified version of them can be found on newer pieces. Early C Clasps were used in the mid to late 19th century until the very early 20th century. The looked just as the name indicates - like a C. Some were just a curved wire which held the pin, and others were a more flattened wider C. In both cases the pin part of the clasp slid under the C and held the brooch in place.
Early locking safety clasps consisted of a C clasp surrounded by a swivel top which was compact and rounded. These safety clasps look quite different from the modern locking C clasps and were routinely used on Art Deco and Art Nouveau pieces in the early part of the 20th century through the middle of the last century. They were patented in 1901.
Trombone or push tube clasps consisted of a barrel shaped on one side of the clasp into which the pin was inserted. The tube moved from left to right for insertion and then slid back to hold tightly. Patented in 1850, they were routinely used in Europe until the mid 1950s.
Safety pin clasps were just that. Small safety pins, either as part of the metal, or embedded in lightweight wood or vintage plastics. Cheaper versions of them are still used, but the most common vintage ones that I have seen are on micro mosaic jewelry and wooden Artist signed Russian pins.
Finally, the modern locking safety clasp was used. You will find it on jewelry from the 1920s until the present day. The construction of it is similar to the early safety clasp, but it has a more "separate" design in the swivel part of the clasp. There are a number of designs of this safety clasp. It has a swivel locking piece over the C, but isn't as compact as the earlier version.
While the pin clasp can be used to give an idea of the age of the piece, once again, it needs to be used in conjunction with other design techniques to give a definitive date of manufacture.
I will examine earring backs in the next chapter of this series. Please check back soon.