Nigel, I agree it's a bit thin.
My thoughts on this patent are simply John Dicksons attempt to improve and reinforce the specification he had already lodged (patent 294 of 1880 for bar slide cocking action, which would go on to used in the round-action).
Remember, Dickson had already found himself in court over the triggerplate design with a dispute with James Macnaughton and his 'Edinburgh' triggerplate design, also of 1880. Dickson won this round and rather than get into further troubles with his Edinburgh 'neighbour' he might want to strengthen his case.
However, there is one other element and that was the influence of Andrew Graham Murray. Mr. Murray was already a noted inventor, sportsman and a customer of Dicksons but at this time he was also a named Director of the company! It is believed that he influenced the construction of the three barrelled triggerplate design for one of his own fancies.
I agree that the number of manufactured three-barrelled Dicksons is in the region of 27 (some records are missing to confirm this exact number and how many actually survive today? I know of only 12) and examples of the side x side x side exist in 12, 16 and 20 bore. Two further exotic examples also exist, two barrels over one and one barrel over two (pyramid design?).
Cheers,
J-PD
