Although I have a large watch collection, I don't have too many Swiss mechanical watches. But today's watch is one of the few!
The watch is by Lanco, which was the most well known brand of the Swiss Uhrenfabrik Langendorf SA watch Company (hence LanCo). The company started in 1890, and the Lanco brand was launched in the late 1950s and then was revived in 1970s, being merged into the Omega-Tissot group in 1971. Production of full Lanco watches stopped in 1973 (as other manufacturers movements were used after this time) . This particular watch is one of the 1970s models, and appears to be after the merger as the buckle shows the capital T which was one of the older Tissot S.A logos.
It is a true jump hour watch, with the hour marker staying still until 2 minutes before the hour change, finally clicking into the new hour on the exact time. The minutes dial is constantly rotating.
It is powered by a 1 jewel mechanical movement by Agon Chromatic Watch Corp, and is designed to be shock resistant. Agon Chromatic Watch Corp (aka Agon SA, or Agon Watch Co) were a private label watch manufacturer from the early 50s to the mid 70s. It was founded by the Triebold family (mainly by Eddie and Othmar, but possibly started in the 30s by their father) in Mumpf, making a large number (it seems maybe millions) of watches and movements. In 1971 the company was taken over by SSIH (the core of today's Swatch Corp), but stopped in the mid 70s when cheap quartz movements came out.
If the items above work out, this watch must have been made between 1973 and around 75/76 as the T on the strap suggests after 71, and the use of a non-Lanco movement, after 73, but must have been before the mid 70s when Agon SA stopped production. So it is actually part Lanco, part Omega/Tissot, and part Swatch!
There is a number 12742 on the back, and as I've seen others with the same number, I assume this is the model number. I don't know the original sale price, but I've seen this on eBay for around £200/$300.