Got the below from Graham Greener on W.W. Greener double barreled hammer gun serial number 21,384:
"Your W W Greener external hammer gun was made in 1879. It is a double barrel, double grip with dolls head extension to the top rib, central fire 12 bore shotgun. It was proved at 12 bore and is choked to 13 bore at the muzzle. The stock does not have a Prince of Wales type grip it is what is described in the trade as a ‘half pistol hand’ and it was this type of grip that was mainly employed on guns intended for export. The gun cost 9 guineas when made or Ł9 and nine shillings in old English money a fairly plain, inexpensive type known later as a ‘Dominion’ model."
