Small Bore. It should be interesting. Plenty of examples to go on. Only yesterday I came across a hammer gun with an 1870 Thomas patent action and a forward facing underlever (straight and in front of the trigger guard) most unusual to see one without the usual top lever. Very handy and just required a short push to the left with the right thumb. Can't understand why it was not a more popular method. Lagopus..... I'll order a book when it becomes available.