Fletch', here's the ones I have from the Index. I do see that my original glance of the Index included one from N Dickson and W Dickson. They read----------
W Dickson 1885 #3928---I cannot find this patent in my abridged book, and it may have nothing to do with John Dickson
J Dickson 1887, # 9399 and 10,621 ---for ejectors and improvements
N Dickson 1908 # 26,031 ---No relationship to the subject at hand
J Dickson 1910 # 21,681 ----With J. Morrison a single trigger.
Sorry for your inconvenience. Oddly the Index I have is somewhat inaccurate . I have found numerous errors. Your # 873 of 1882 , which is a J. Dickson and A G Murray for the three barrel gun do not show in my index, under Dickson, but do show under Murray.
J Dickson # 294 of 1880 does not show in my Index, but I find it in the list of 1880 patent abridgements.
So much for reading and believing all that is written. Sorry for any inconvenience. Daryl