Right gunman, my fault, it was Scott Improved Greener Bolt, my bible says Greener-Scott Cross Bolt. Also I found in the same bible two fine drawings of hammer Purdey double and Scott double with square bolts.
In Bitkoff catalog of 1912 I found several guns with square bolt made by Aug.Lebeau, ManuFrance, Lepage in Liege, F.Demulen, Pieper.


Geno.