Info on plug 8

My father has a pair of handcuffs that came from his grandfather. He has always called them "slave cuffs", but after I researched a little, I know they are plug 8s.
The only markings on them is a lower case "f" and a number "2" stamped on the end opposite the cylinder. The key looks like the Froggat's.
Is there a way to find more informaton on these?


Thanks,
Paul