Oyster Perpetual is a simple time-only wristwatch by Rolex.
By definition, “Oyster Perpetual” is a simple time-only model at the low end of the Rolex lineup. The name comes from the trademark waterproof “Oyster” case and the “Perpetual” automatic movement. The company's naming scheme makes every watch with these features technically an “Oyster Perpetual”, but Rolex no longer uses these long names for models like the Submariner. Instead, the Oyster Perpetual name is applied to differentiate time-only watches from models like the Datejust, Day-Date, and so on.
The Oyster Perpetual line includes models for men and ladies, and has featured many different designs from sports to dress. The current lineup includes five case sizes Oyster Perpetual 39, Oyster Perpetual 36, Oyster Perpetual 34, Oyster Perpetual 31, and Oyster Perpetual 26.
Historically, the Oyster Perpetual was available in 34 mm (men's) and 26 mm (ladies) sizes. These are the equivalent of today's larger Oyster Perpetual 39, Ref. 114300, 36, Ref. 116000, and 34, Ref. 114200, and the smaller Oyster Perpetual 31, Ref. 177200 and 26, Ref. 176200.