Union Firearms Co. hammerless appears to be a sidelock
CZ,
There are two variants of the Colton and at least two Union SxS models also. Don't know about the early Colton or the late Union model but the two guns I have are very similar.
I had always assumed the Union SxS's were a hybrid lock. Your post got me thinking so I grabbed each (Colton & Union) and pulled a plate.
Unconventional, but a sidelock.
Colton(top) and Union F.A.(lower) doubles. I believe the Union to be a Model 22.
P_20170926_200642 by
John Eurom, on Flickr
The Colton: Coil spring with inline hammers. Floating FP in frame.
P_20170926_201131 by
John Eurom, on Flickr
P_20170926_201235 by
John Eurom, on Flickr
Union F.A.: Much the same as the Colton but the cocking bellcrank is mounted to the lockplate also and the parts are secured with a bridle.
P_20170926_201600 by
John Eurom, on Flickr
P_20170926_201657 by
John Eurom, on Flickr
The mechanism is somewhat unique, wouldn't you all agree?
John
