The movement is a Landeron 248 and fitted with 17 jewels.
http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Landeron_248
https://watchguy.co.uk/service-bucherer-chronograph-calibre-landeron-248/
https://forums.watchuseek.com/f11/landeron-248-movements-yes-both-1285850.html
https://forums.watchuseek.com/f11/landeron-248-info-needed-53568.html
Cheers! Should have looked into it myself but quickly spotted it on my phone whilst away with shoddy internet
@bobble started
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http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Landeron_248
https://watchguy.co.uk/service-bucherer-chronograph-calibre-landeron-248/
https://forums.watchuseek.com/f11/landeron-248-movements-yes-both-1285850.html
https://forums.watchuseek.com/f11/landeron-248-info-needed-53568.html