All-
In looking for something else I sorted my inbox and found some parts of this thread that I didn’t see before. The enlargement of the Wm. Osborn shows, I think, a standard CB&Q F class (later G1 /G2) 0-6-0.
The record is not clear (at least to me at this point) if all these were built new as such or, as it seems at least some were heavily rebuilt from very early 4-4-0s.
At any rate, they were, along with the E Class 0-4-0s, the first dedicated switchers. They came after 4-4-0s that were downgraded for switching, although 4-4-0s were built that way without tenders very early on.
The CB&Q did end up designing and building the G3 and later G6 modern (for 1900) 0-6-0s which shared many parts with the R Prairies These were augmented with converted D class and later R class engines to 0-6-0s.
Charlie Vlk