The Heuer Autavia 3646, with 1st execution dial and 2nd execution hands, was produced with a stainless steel screwback 38mm case. The serial number is engraved in between the lugs at 6 o’clock.
Caseback
This case has written around the caseback
STAINLESS STEEL CHRONOGRAPH –
WATERPROOF – GUARANTEED 330 FT UNDER WATER –
Then, centered on the caseback, about 1/3 of the way from the edge, is
AUTAVIA
[Heuer logo]
The exception is for the few ‘KINGON‘ branded pieces we see, where ‘KINGON’ text is below AUTAVIA instead of the Heuer logo. The text style for these pieces is different than what we see on the Heuer-logo casebacks, as they were likely delivered blank and later engraved by/for Kingon.
Some casebacks will have a ‘C’ number, which is in the pattern ‘C xxx-x’ or ‘C xxxx-x’ (I haven’t seen others with fewer numbers, but presumably these exist). This number was used by Cuanillon & Cie, the company that was Heuer’s Swiss distributor. I have not heard of records from Cuanillon, but it is believe that each C-number was unique to a watch. If you know of records, please contact me.
Inside caseback
The inside caseback has a few different designs. With so few pieces known, I have very little information on inside caseback stamping.
I have seen multiple pieces with each of the following inside caseback design:
1. Slightly above center (488xx-489xx):
ED. HEUER & CO S.A.
SWISS
2. Toward the top of the inside caseback, about 1/4 way down from top edge (522xx)
[Heuer logo]
ED.HEUER & Co
SWISS
There are two additional inside caseback stamping examples I have seen. As I have seen only one of each, I will hold off to providing images.
1. Toward the top of the inside caseback, about 1/4 way down from top edge (1 piece, 488xxx):
ED. HEUER & CO SA
SWISS
2. Starting toward top of inside caseback, extending all the way to below center (1 piece, 487xx):
[Heuer logo]
ACIER INOXYDABLE (or ‘INCXYDABLE’)
[Huegnin Freres logo]
ED.HEUER & Co
SWISS
The case of the 3646 was modified during the period with the 2nd execution dial (I believe those pieces have wider bevels).