Yours is referred to as the 2446C and is a different model. The serial number is stamped between the lugs.

: I have recently seen 1967 Autavia fetch £20,625 at a Bonhams
: auction. I have a similar watch, the only difference I can see
: is that mine has a snap back whereas this one was screw back.
: The sold model had a case No 86068. Where do I find the case
: model number on my watch which I purchased in 1968? I still have
: the original box and instruction manual.