The ‘Beta 21’ movement was first created in 1969, and made its debut during Basel later that year. At the time, the Beta 21 was revolutionary as it was the most accurate quartz movement to be offered on the market, and accurate to 5 seconds per month. Due to the movement's large and bulky size, watchmakers soon developed their own in house movements and gradually moved away from the ‘Beta 21’.

The reference 5100, or the ‘Beta 21’, is a landmark reference for a number of reasons. Launched in 1970, it was Rolex's first reference to carry a quartz movement. Rolex first produced 1000 units to test the ‘Beta 21’, and all examples were sold out before the watch even hit the market. The 'Beta 21' was also Rolex's first reference to feature a sapphire crystal and quick set date function – two key innovations and components that are used in Rolex's current line of production.

John Goldberger's Opinion

I think this watch is rather remarkable, as it is signed 'No. 1007' to the case back, and one of the very last examples ever made. Rolex quietly produced a very limited number of examples after releasing the first batch, attesting to the popularity and innovation of the reference.

The case is preserved in excellent condition, with strong gold and hallmarks to the right band. The proportions can only be described as excellent, with sharp facets to each side of the case.
Interestingly, two different kinds of bracelets were fitted to the ‘Beta 21’. The present example features the second-generation bracelet, which is correct for the late case number.