The Rolex reference 5100, known as the “Texano” or Texan, is Rolex’s first quartz wristwatch. Launched around 1970, it has a solid 18 kt gold case of roughly 39 to 40 mm with an integrated gold bracelet. Inside is the Beta 21, an electronic quartz movement developed by the Swiss Centre Electronique Horloger consortium, with a sweeping seconds hand and an accuracy rating of about five seconds a month. The case was not a full Oyster; sources describe it as moisture resistant, not waterproof.

Production numbers are usually given as around 1,000 pieces, mostly yellow gold with about 100 white gold, though sources disagree on the exact count and on the production dates, which run from 1970 to around 1972. Each case was individually numbered, and Rolex later replaced the 5100 with its own quartz movement in the Oysterquartz.

The Texano is among the rarest Rolex references and a landmark in the history of the quartz revolution: the Beta 21 was the first Swiss quartz movement, and the 5100 was the first Rolex to use it. The community values it for that rarity, and prices in the tens of thousands of dollars are common. It is long out of production.