Nice to find you here. You should find a calibre 12 400 inside. I'm not sure about how original the dial is. You'd need a loupe or we'd need some macro photos to advise you.
The knock off pin buckle does seem to raise some questions about the watch. It would be nice to have an Extract from the Archives or other service papers if they are available.
I always liked a simple manual wind pp .. Plus I love the fb screwback case in 18k to boot...
I have others by other makers like movado , alpine , mido ...
The case is tops in my book .
Simple ... But the broken swan neck might be the straw , as it is hint that a possible low end watchmaker "repaired " this and that just might be the tip of the iceberg
Bill, I also love the 2509, what a great, classic look with a bit of flare - great batons! Check out the 2508 with pyramid markers, it may steal your heart