[cameleon]

Thank you for your answer JS, but if I had the possiblity to photograph, I would have done it but I do not have a numerical apparatus, however I will refer according to your council towards
technical information, but I have hardly hope to find there the answer. I have tried to clear up this mystery, with many gunsmith and collectors in France, but nobody could bring an answer to me. I will try to make a drawing representing the enigma.