Harold- The barrels on mine are damascus, I do see a difference in the profile of the lock's curve at the breach, but the engraving looks very similar. the location of the release lever seems to be the biggest difference
a link to my album
http://parkerguns.org/forums/album.php?albumid=720
here is an excerpt from my letter
"W W Greener gun no. 12964 was made in 1873. It is a double barrel, shotgun with external hammers and push-down breach opening lever. Proved at 13 bore in Birmingham, England and stamped with proof marks of the period 1955 – 1875 the 13 bore is nominally a 12 bore and as such is chambered for standard 2-1/2 inch 12 bore black powder cartridges. It is not suitable for modern nitro cartridges which burn much faster creating greater pressures in barrels and action.
The gun appears to be a ‘Snap-action’ breach loader with one holding down bolt within the action – I will be able to confirm this on receipt of a side view of the barrel lumps. It has bar-in-the-wood side-locks and is very similar to many side-lock hammer shotguns made by W W Greener between 1870 and 1874. Several thousand of guns of this type were made and so they are fairly common, however, you gun has one feature I have not seen before in the design of the push down lever which is partially wrapped around the trigger guard. In this respect it is rare, if not unique since I have never seen one exactly the same as this before. The normal push down opening lever is fashioned so that it is positioned on the side of the gun alongside the right lock (for a right handed person) and not underneath the trigger guard – photo of similar W W Greener gun attached showing the normal configuration of the breach opening lever."