Hamilton 505

Significantly improved version of Hamilton's electric movement, released in 1961 to address reliability issues with the original Model 500. The delicate contact wire and trip spring were eliminated, replaced by a non-adjustable contact on the balance assembly, making it simpler and more reliable. The trade-off is stronger contact pressure leading to faster contact wear. Used in later Hamilton Electric watches including Ventura, Pacer, and other models. Production ceased in 1969 with the advent of quartz technology. Modern 387S batteries are compatible with this movement.