This is a Zabala Derby imported by American Arms, not sure when.
It is a 6 pin (only 5 are used, it has a coil mainspring and the other pin is a dummy), cocking indicators, single non-selective trigger, auto ejectors that use the Southgate syle, hidden second bite,bushed firing pins with gas ports, straight stock with a checkered butt. Weighs 7lbs. .08 ozs with 26" barrels and 7 lbs. 3.6 ozs. with 27 1/2" barrels
I bought a spare set of barrels and fitted them. The barrels that came with it were 26" imp.cyl/mod. These are 27 1/2" and are mod/full. No proof marks or any other marks on the new barrels, but all information on the other set.