Predating the Constellation was the Omega Centenary ref OT2500, Omega’s first chronometer wrist watch introduced in 1948 to celebrate the company’s 100 anniversary. This Omega 2500 predates the Centenary by 2 years as it was introduced in 1946. Although the 2 watches share a similar dial they are not the same watch, look at the 2500 as more of a building block that eventually led to the acclaimed Constellation. This watch is in excellent condition and is cased in 18k yellow gold. When it comes to rare collectible Omegas this one is right up there.