Hi Lee

,
thank you, so much, for your reply and the information.....and sorry for the delay. Would you mind posting a scan of some of the 'similar' knives, I have had difficulty in finding images.
Hi Stekemest,
I did consider one of the objects as a broken key....but the 'loop' is flat (in cross section) and would not be comfortable to 'turn' (as a key) as the edges would 'dig into' the fingers.
I have continued to search for a similar marking (on the knife) ....but have been unsucessful. (searching ALL eras ie Medieval onwards)
Kind Regards David