Welcome to the forum Bo!

We need some pictures to be able to give you any definitive answers, but there are a couple of things to share.

The Carreras never used the Valjoux 21/2/3 though some of their predecessors did. The earliest Carreras used the Vj 72 (Carrera 12, the 3-register models) and Vj 92 (Carrera 45, the 2-register models). You might tell from that name that those 2-reg models have a 45 minute capacity rather than 30 minutes. The Carrera 30s didn't come in until around 1968/69.

Sounds like your watch might be one of the so-called pre-Carreras but we need photos to really help. You'll need a photo host (lots of free ones like Imageshack, Photobucket etc), then follow the guide at the top of this forum. If you struggle with that, you can send them to carrera_table_mm@btinternet.com and I can host and post!