I have correspondence from Peter who is very familiar with these engines. He owns a 7 ¼ inch gauge live-steam example and provides this analysis of some of the class features as distinct from the later C17.
Peter says in an email: "The C16 has slide valves
on the cylinders ( due to saturated steam on a C16 ) whereas the C 17 has
piston valves on the cylinders ( due to superheated steam on a C17).
The loco in the picture has a MASTER MECHANICS smoke box as evident by the tapered chimney. These were fitted to some C 16 ‘s late in life to try to improve their steaming efficiency. C 17’s never had this conversion or chimney.
C 16’s built before 1914 had the cab side opening (where driver would lean out) with the curve at lower front. Then they had the straight rectangular type of
opening on the cab sides. C 17,s had the rectangular opening from the first one built. In later versions they had the sedan cab & roller bearing axles. (These were known as Brown Bombers because they were painted a plain brown with a green trim)." - End of quote from Peter.
I had thought for some time about publishing my album photos, even though they are not top quality. And perhaps mixing them with some others from friends I know in a joint booklet. But posting them on the internet is so much easier, and gives me the same amount of pleasure. I know the images will have a far greater audience as well.