Rolex Submariner Ref 1680.

The Rolex reference 1680 is an outstanding vintage watch model. 

This example features a 3.9M serial number and dates to circa 1975. It is paired with a reference 93150 Oyster bracelet with a CP clasp code It comes with the correct 580 end-links. The insert is ghosted.

The dial appears to have been relumed in the past. The hands have been relumed. The case has been polished. 

If you are looking for a vintage Submariner that is not expensive, this is a very fun watch.

The lug-to-lug length is approximately 47mm, and it measures 40mm in diameter, excluding the crown. 

To learn more about the Rolex Submariner, you can read Eric Wind"s ‘Reference Points: Understanding The Rolex Submariner’ article and corresponding video.
We do not know the service history, but it is running well. The watch does not come with box and papers.