Triskelion

A triskelion shape was used in the design of RCA’s “Spider” 45 rpm adapter, a popular plastic adapter for vinyl records, which allows larger center-holed 45 rpm records (commonly used on 7″ singles and EPs) to spin on players designed for smaller center-holed 33-1/3 rpm records (the standard for 10″ and 12″ LPs).

 The design was practical, the three curved arms providing equal spring and thus keeping the hole centred. 

The iconic design of the Spider has led to its adoption as a popular symbol for record and music enthusiasts.