The makers mark is under the balance, you should be able to hunt it down from that.
Looks like an Amida, but I can't figure the caliber.
More info has been provided courtesy of this researcher.
http://www.toffsandtinks.com/shop/Amida-SA/info_53.html
Amida S.A.
Amida S.A., a Swiss watchmaking company, operated in the heart of the watchmaking region at the foot of the Jura Mountains from the very early years of the 20th Century, possibly earlier. Historical information is scant, but various brand names and trademarks are linked to the company and manufacturing locations were recorded at Biel, Longeau and Grenschen (Granges, as in the above advertisement, is probably the French-Swiss name for the town of Grenschen, which is the name used by the German-Swiss. However there is another Granges north of Montreux beside Lake Geneva which was also a watch-making region but it seems unlikely that the company would operate in two geographically separate regions). The company produced its own branded pocket and wrist watches, but as the illustration above from a 1939 copy of La F茅d茅ration Horlog猫re Suisse shows, it was also producing 茅bauches, or base movements and part movements at Granges (Grenschen?) for supply to other watchmakers who would rebuild these to their own requirements and specifications. This was common practice in the Swiss watch industry and although Amida was never in the top flight of Swiss watchmaking, the innards of some very expensive brands often started life in the workshops of more humble and lesser known companies such as this.
Brands manufactured or supplied by Amida S.A. in addition to their own Amida brand include La V茅rit茅 and ReVox, the latter now owned by the SWATCH Group. I have so far been unable to ascertain whether these brands belonged to other companies and were assembled from 茅bauches supplied by Amida S.A. or whether the brands belonged to Amida S.A. and were manufactured in-house. There is a suggestion that Charles Abrecht S.A. a watchmaker in Biel, may have been linked to the La V茅rit茅 brand but so far I have been unable to establish the precise connection.
As far as I am able to establish, Amida S.A. no longer exists, probably a victim of the 1970s quartz revolution from the East, and the last watch produced by the company was the rather avant-garde digi-mechanical Digitrend in the 1970s, a "jump-hour" type which built a cult following which continues today with good examples fetching surprising prices.
The brand marks below are all associated with watches manufactured by Amida S.A.
Mark/Name Summary Information
This trademark, an A within an arrowhead, is associated with the manufacturer's own brand name Amida. Watches, watch components, and housings were manufactured at Grenchen, Switzerland. The name and mark were registered on 25 May 1938
The name Chronometro Verdad/1A is associated with the brand mark to the left. Watches and parts were manufactured at Grenchen, Longeau and Biel, Switzerland. The Biel association may indicate a connection with Charles Abrecht.
Cronometro Verita
Watches and parts manufactured at Grenchen, Longeau and Biel, Switzerland. There is no associated brand image. Comments as for Chronometro Verdad/1A
V茅rit茅
Watches and parts manufactured at Grenchen, Longeau and Biel, Switzerland
Comments as for Chronometro Verdad/1A
Watches and parts manufactured at Grenchen, Longeau and Biel, Switzerland, registered on 27 January 1925. The trademark may have belonged to Charles Abrecht S.A. of Biel.
ReVox
Watches and watch parts manufactured at Grenchen, Switzerland which might suggest this was an Amida S.A. own brand.
Further research is required to extend and verify the information given above. If you can provide further details on this company, its ownership, dates of operation, collaborations etc, or make any corrections, I would be glad to hear from you through the Contact Us option below.