There have been several discussions about 3-frame 12-gauges on the PGCA web site -- http://parkerguns.org/forums/

My Grandfather's 1890 vintage Parker is a 3-frame PH-Grade 12-gauge that weighs a hair over eight and a half pounds, with 30-inch barrels that swamp in very fast. I have an 1889 vintage GH-Grade 12-gauge on a 2-frame that has barrels with virtually no swamp and weighs in at a shade over nine pounds. The Brothers P with all their frame sizes did some weird and wonderful things with weight and balance.