Gunman it totally correct, the screws on the flats are the retainers for the cocking rods which form part of the Perkes patent that you mention. This patent was bought by Scott and worked extensively by them. You will see it in early H&H No.2's, C&H and Blanch backaction SL's amongst many others.
If the gun is sleeved, the absence of any marking of 'sleeved' puts the gun out of proof by UK proof law. It might have been stamped on the barrel flats or on the side of the barrels and been struck out or maybe the gun was sleeved in the USA where of course no marking is required.
A44, you can always spin out those screws to remove the plate, they don't do anything else. Just make sure you have a well fitting turnscrew.
