That's not a Breitling reference number

That's one of those watches that have been assembled from Breitlingparts from the stock, after the production was not properly 1975-79 or after 1979.

I've seen a few of this exact watch on ebay over the years and really can't see anything that would indicate it's a fake. There's also a gold case variant. Just another anomally from a turbulent time in Breitling's history.

I think it is more accurate to say that it has been assembled using some Breitling parts and some non Breitling parts.

I think that case is quite similar to some '70s Heuer Autavias.
Those watches are real nice.

I don't know of a pre-1979 Breitling with a Lemania movement. I've been hunting in my literature and can't find one. Richter has the biggest list and he doesn't show one. It could be, but it seems odd for Breitling to use an Omega/Lemania product instead of an ebauche.

In the eighties at least so no real reason not to think it's a possibility since the 1873 came into existance around 1968.

"The movement is what makes this watch so special. The Callisto Chrono is powered by a Breitling Caliber 11 movement, which is a manual wind chronograph. It is the 12-hour version of the more well-known Caliber 12 movement, which was used in the Breitling Cosmonaute II.

These movements are based on the Lemania 1873. The Callisto Chrono uses the regular movement, whereas the Cosmonaute sports a 24-hour geared 1873 (so that the hour hand makes a full cycle in 24 hours). Those movements were used by Breitling from the 1980s until in became unavailable in 2002."