These models were very expensive when new. The Bulova patented electric (not quartz) movement had been proven over time, and Omega (among many other makers) decided to produce a wide variety of models with the “Omega” caliber 1250 inside. No other movements have a smoother seconds hand! The serial number starting at 34 million puts the production date to first half of 1972. The Renata 344 battery fits these watches well. To ensure accurate and durable running, the battery should be fresh (and changed as soon as any slowing occurs). The date change is easy, there is a middle position on the crown.