Hi Frank, welcome to OTD. You are correct that it is unusual to see a (modified) calibre 11 in a GMT but not unheard of. It is recognised that the early 1163 GMTs used the cal.11 but there do also seem a few 11630s that used it also-a couple of which can be seen here-

http://www.chronocentric.com/forums/heuer/index.cgi?md=read;id=86957

and here-

https://www.bonhams.com/auctions/24883/lot/55/

the latter being the most interesting as the serial is also 262xxx.

So while not being the norm, it is not totally unique in that sense.

Hope that helps,
Steve

: Hi. I’m new to the website and looking for some information on a
: watch I recently acquired. I’ve posted some pics but what
: I’m confused about is that most of the gmt’s I find online
: have the Calibre 14 movements but mine has the Calibre 11 in it.
: Any help is much appreciated as I eventually am looking to sell
: it and want to make sure I’m posting it correctly. The serial
: # is 262xxx

: https://ibb.co/LYkYymT
: https://ibb.co/xLQVds2
: https://ibb.co/ggdqTzW
: https://ibb.co/JRj3d94
: https://ibb.co/dJvf0xg
: https://ibb.co/hKg4yLp
: https://ibb.co/P6SCNM2