Only one with a 16 beginning...

: All the Carrera 1553s I have seen have had cases correctly marked
: 1553, rather than reusing 1153 cases.

: I suspect this comes down to volumes as much as anything - we have
: heard anecdotally from Jack Heuer that the Monaco at the time
: was not a runaway success, whereas the Carrera and Autavia had
: longer histories for Heuer to estimate sales against and were
: selling strongly.

: There are other occasions (hands, markers) where Heuer seems to
: "use up" existing stock of components even when they
: have a new or redesigned model, and it looks to me like the same
: thing is happening here with the Monaco cases. The situation
: isn't quite the same, as the Cal 15 models were intended to
: complement, not replace, the Cal 12s. What would be interesting
: would be to compare serial numbers to see whether they used 1133
: cases at the start before 1533 ones were available, or once the
: initial batch(es) of Cal 15 cases were used up.