Trombone Catch

Trombone catch on a vintage brooch
Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals
The trombone catch is a type of safety catch used to secure the pin of a brooch.

The trombone catch was invented in 1910 and features a slide mechanism that secures the tip of the pin.