A timepiece (1) including a middle (110) and an interchangeable bezel (200) fastened to said middle (110) by relative rotation of the bezel (200) relative to the middle (110), about a central axis (B), between an interlocking position and a locked position, by a bayonet fastening device (300), said bayonet fastening device (300) including first fastening elements (300a) formed on the middle (110) and second complementary fastening elements (300b) formed on the bezel (200), wherein the bayonet fastening device (300) includes a mechanical coding system (210, 116) for defining a single position in which said bezel (200) can be interlocked with the middle (110).

A watch body and a strap are included. The watch body includes a case body having a cylindrical shape, a movement disposed inside the case body, a cover member covering one opening of the case body, and a case back covering the other opening of the case body and including a transmissive region through which the movement can be visually recognized from the outside and the movement can be visually recognized through the cover member. The strap is attached to the watch body and includes a base facing the case back of the watch body and a strap body coupled to the base. The base includes a decoration at a position overlapping at least a part of the transmissive region, and the decoration can be visually recognized through the cover member.