Pocket Watch - Diamond & Platinum

The following Vacheron & Constantin pocket watch is featured in an late November, local auction and I'm curious if anyone knows anything about it.

The circurlar case has arabic numerals with rose cut diamonds (numerals on the case, not the dial) and features diamond-set hands.  Early 20th century, 44mm diameter. The case back is signed V & C (but not displayed in photos) and the movement is signed Vacheron & Constantin with 18 jewels (again not identified in photos).  The auction listing does provide the serial number.

I can't find any references to BRÜDER KLEIN BRÜN that features on the dial (here or in Secrets of Vacheron Constantin).

Thoughts?

Pocket Watch - Diamond & Platinum
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