Tudor Oyster(date) ChronographThe Chronograph is the pillar of the Tudor production. The first ones were created in 1970 and called 'Montecarlo' for the dial graphics which are simular to the casino chips. They differ from one another only by the type of bezel; the case, with srew-down pushers and winding crown, is amongst the sturdiest ones on the market. The movement, initially with manual winding mechanism, was replaced with the self-winding movement caliber Valjoux 7750 in 1977, which will stay in this model over the course of its lifespan. In the 80's and 90's, the "Rolex style" timepiece of the Tudor chronograps achieves great succes and the excellent price/ quality ratio makes them interesting to the public. Cases are modified in 1995; they become thinner and the plastic crystal is replaced with the sapphire one. The 1997 is the last year in which Rolex signes the Tudor cases, which change from "Oyster Date" to "Prince Date". The two brands begin to diverge and the chronograph , which is substantially unvaried, continues to be produced until 2005.