Researching on the cal 30T2 led me to cal. 265/266. I understand that these 2 calibers were derived from the 30T2. Running a search on Ebay for 30T2 comes out with results which I looked up on the Omega database using the case ref. And the results show that they are actually cal 265/266. Are the sellers actually correct to state 30T2 in their listings? Or is it acceptable to use them interchangeably? And also, I assume that the 30T2 is more collectable than cal 265/266. Is that correct? Appreciate your thoughts on this.
They really should not be used interchangeably. A 266 should be described as a 266. The 30T2 has several forms (and predecessors) depending on its use and from different dates during its developmental time period and has given rise to over a dozen sucessors. Specific 266, 267, 283, etc., may or may not be more valuable the a specific older 30T2, it all depends on the watch reference, age, rareness, condition, etc. Certainly a 30T2 RG or 30T2-SC-RG chronometres are considered highly collectable and usually garner a high premium. So collectable depends on what you are collecting at the moment. This is a very superficial explanation and you are on the right track with your reading.
These movements fall under the guise of 30mm omega manual wind movements - either subseconds or center seconds. Outside of the Rg movements as Steve pointed out and perhaps the very first batch of 30mm movements the various movement varieties do not make a difference in price - condition being equal of course. The case style, size and material as well as the dial style and overall condition are more important in terms of final valuation rather than which 30mm movement is in the case. I would add that for a mass produced brand, the variety omega has shown with this movement is staggering - I wouldn't be suprised if there were over 1,000 different and distinct models housing one form of the 30mm movement or another.
As a collector of the 30mm, I focus on the 30's with early serial in 8 mil range , the Rg's, the 30T1SC (only 2400 were produced ) and the T2's with 18 jewels. a 30SCT1 a T2SC with 18 jewels 30T2Rg with "adjusted five (5) positions and temperature (prefered )
The 30mm series was produced for almost 30 years. There were many changes and refinements made over that period of time. A good analogy would be to think of the ebauche (movement plate) like the engine block of a car. For years, Chevrolet used the same engine block for vehicles ranging from economy cars to Corvettes, just making tweaks to the tuning and performance parts as they moved up the cost chain. Omega did much the same thing. The basic 30mm movements (cal. 30T2, 26X and 28X) were very good for mid-price manual price watches. My watchmaker once told me that they practically reassemble themselves, they were so easy for him to work on. When Omega added some of the performance touches like micro-regulation, Breguet overcoils, etc. to the basic movements for chronometer certification, the performance was award-winning. Take care, gatorcpa