I think it is probably French, or French style. And no, not a Kunz. While the border engraving is similar to the Kunz shown, that was a popular style, back then, and now.
Original or Reproduction? It looks in great condition, and not all rusted together. So I'd take a tight fitting screw driver and see if you can wiggle one of the screws loose. A little WD-40 would help. On an original, a screw from this time period will most likely have course threads, and not the fine threads you see today. Also, any file marks on the parts? Guys today tend to polish all the file marks away, guys back then tended not to.
Either way, it's a nice looking lock, and like Mark, wouldn't mind having it!
PS, as for English pans, Ketland made some detachable ones.
John