This is a charming Helvetia watch, coming from the UK for a service.
It has an in-house movement as most of them do. In this case, it’s the Helvetia 830 with an unusual design.
The ratchet wheel, the crown wheel, and the click are “hidden” underneath an extra cover. This movement also has an intermediate wheel between the 4th wheel and the sweep second pinion.
It’s always fascinating to see something that isn’t like most movements and it keeps it interesting.
The watch is from the mid 1950s.