Dan,
I have seen a couple of those shaped lockplates on early Hollands and actually restored one a few years back. The lockwork is classic Scott of the period and I guess that the slightly unusual lockplate style was the characteristic of the trade gunmaker who was supplying Hollands at the time.
Here is a photos of the one I handled:
And at the time I wrote the following about it:
This is an extraordinarily rare 'No. 2 Pattern' sidelock specified with 'Best Finish'. We have never actually seen one of these beauties before nor know anybody who has. One should note the very unusual scalloped lock plates and the lack of any through pin in the lockplates. Also the very broad action, almost a pigeon gun in its proportions.
The lock internals are pure early 'Royal', which it predates, but with no dip to the upper edge it looks much more like a later 'Royal' in profile. It was built as an ejector utilising the notorious Hodges ejector patent and so one can assume it was actioned by the EC Hodges who was a very important 'actioner' to the London trade. However, the ejector system was changed to the much more reliable Perkes system, probably around 1890.A link to the gun's details is:
http://www.heritageguns.co.uk/H&H%20SLE%207817/H&H%20SLE%207817%20Details.htm
