That's a very early 3647T. I am not an expert in when the serial range began for the T version. I can tell you that my 3647N is serial 5456X and from the research I have done, it may be the earliest 3647N known at this point. There are at least two 3647S models that are earlier than my 3647N, including the one referenced in Eric's wonderful article. Hope this helps. I would love to learn more about these earliest 3647 Carreras - I think they are perfect from a design perspective.

Jim

: A couple of months ago I started a thread regarding a 3647T.

: http://chronocentric.com/forums/heuer/index.cgi?md=read;id=76766

: I had it sent to my brother’s house as I am abroad, and finally
: after a few months I got it in my hands yesterday..

: Will try to take some decent pictures tonight and add them to this
: thread.

: I think the serial number is quite low for a two-register Carerra
: (5476x), which would make sense for the Swiss only dial and the
: Ed Heuer signed bridge on the movement. How low do serial
: numbers go for the Carrera 45 (3647T) specifically ? I saw in a
: Hodinkee article that the earliest known two register Carrera
: was 54510, is that still the first known one, and would it have
: been a 3647T or they came later ? I was wondering (wishfully!)
: if perhaps the mis-alignment of the Swiss on the dial could be a
: sign of an extremely early one ?