Hamilton 500A

Modest improvement over the original Model 500, introduced in 1959. The wire battery clip was replaced with a simpler clamp design, and the shockproof jewels were modified. Otherwise virtually identical to the Model 500, retaining the same critical contact wire/trip spring assembly. Still requires extremely precise adjustment of contact wires. Used in Hamilton Electric watches during the transition period before the significantly improved 505 movement was introduced in 1961.