Certina (Kurth Frères SA) is a underestimated brand that made great quality in-house movements right up to the quartz crisis of the 1970’s. A cool thing about Certina is that you can date your watch by looking up the serial number. There is also write up on the kurth frères/Certina history here. 

1951 Certina Case ref: 8721.1. Calibre KF320. Serviced March 2022. Case size 33mm w/o crown. Asking price £280 Click on image for more photos.  

Pre Turtle back (1958-60) Certina DS. In-house calibre 25-36. Very good condition. Serviced by me Febuary 2018. Case size 36mm w/o crown. Asking price £ 580