P V Spring frame

Here's one of the first attempts at motorcycle rear suspension. The "swinging arm" pivots around the end of the frame stays, the front loop has a sliding block that moves around the curved frame tube with springs above and below to control wheel movement. 
Elliston and Fell introduced this rear suspension in 1910 on the P V (Perry Vale, named for the location in London of the factory). Later versions moved the springs inside a slotted larger diameter tube for a cleaner appearance. The company was gone by 1925.