Armstrong 40pdr: elevation mechanism

As I mentioned in my 3 April post, the mechasnism by which the 40pdr is elevated needed investigation. I spent a bit of time with my search engine, which revealed a possible answer, but features in the contemporary photographs of the 1882 armed trains raised a question.

Wikipedia has a commons library for the Armstrong RBL 100pdr, with photographs showing a Smith's Elevating Screw mechanism (see the link that follows) below the breach. However, the photographs of the armed train show a pair of what appear to be levers, fitted to the left and right sides of the gun carriage.

I need to discover how these functioned before I commit myself to modelling the mechanism; it’s possible they operated screws and rods for drawing a quoin (an angled block) forwards or backwards to depress or elevate the barrel.

Further search engine work surfaced this rather handsome 1/9 scale model (the videos are particulary impressive):
.778" Bore 110 Pounder Armstrong Gun

HMS Hecla 1882: one of the levers on the side of the Armstrong RBL 40pdr carriage, improvised by the ship’s crew.

HMS Warrior: what appears to be a ratchet mechanism beneath the breach of the much larger Armstrong RBL 110pdr. (Wikipedia commons)