A watch that's actually close enough in age to legitimately be called a pre-Carrera - I'm not sure the 2447s et al should be called that, as there is more of a disconnect between them and (the confusingly named) Carrera 2447. The tachy scale is more or less exactly as used on the first Carrera tachies too.

They're not exceedingly rare but we don't see many of them - they were around at the end of the 50s and sold alongside the Autavia after that was launched, but the pretty much immediate success of the Carrera made them more or less redundant. So they had a run of 5 or 6 years, during which time production was slowly ramping up. There must be a few about, but there was a spate a few years back of amending the dial to say Carrera in an attempt to add (perceived) value. It might have caught out some of the unwary (there are a few otherwise notable collections that have or had one in, sometimes called "prototype" Carreras sadly), but by and large it just devalued the original watch.