I agree with what Heinz and John have written, and confirm that we see many of the vintage Heuer chronographs that "sat on the shelves" of the retailers for relatively long periods. For example, it would not be unusual to see a chronograph that had been produced in 1977, have a receipt for the original purchase dated 1981. Also, I do not believe that Heuer attempted to update specific models from one year to the next, but it might have added a couple of models or executions to its catalog, in a given year.

Jeff

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: Hi everyone, I don't know if this helps with your question but here
: is my experience. I purchased a Heuer Autavia GMT 11630 , Serial
: # 31476/54 on June 05, 1975 from a long time Heuer dealer in
: Zurich, Switzerland. I was visiting my Dad and as usual I
: stopped by to see the latest from the Heuer line. The dealer
: told me that he had received this watch about a month ago from
: Heuer. If I recall correctly the going price was about 220.00
: Swiss Franks. Considering that I had purchased a 1163 model
: earlier here in the States for US $ 135.00 , I thought that this
: was a good price for the latest model with mineral crystal, SST
: band and spare bezels, (Tachy, Decompression and 24 Hr.) As
: mentioned , this would not pin down the exact production date
: but put it in the ball park of earlier in 1975. Hope this is of
: some help. All the Best. Heinz Rengel.