Um welche Art Beschlag bzw. Scharnier handelt es sich hier ? Vielleicht von einer Buchschliesse bzw. von einem Buchbeschlag? Größe: 1 x 1 cm

Hallo Tablifer!

I think your  find is a part of folding strap clasp (called folding end) dated e.g by  R. Whitehead to 1350-1450....
....at least the dimensions and shape fit perfectly to that hypothesis 

Cheers
Pawel

Hi Pawlor,
Thanks a lot for your reply. Your hint on the book of Whitehead lead me to take a look at G. Egans book and it seems, that you are right.
Kind regards,
Tablifer