I'm really patchy on 50s Heuers. Others know a lot more - Jarl is one of the "go to" people for Heuers of this era.

They do seem to be some of the watches that are still available relatively cheaply, though, as I think it's an era many of us have yet to discover. There does seem to have been quite a lot of diversification in the 50s, with less of the strong focus on chronographs we see throughout most of the rest of Heuer's history. Some DNA does seem to be carried forward more or less intact, such as in the perpetual calendar watches but others seem to have reached dead ends and remained in the 50s.

I think they are on the smaller end of the watch size cycle in the 50s - think more first generation Carrera than late Autavia.