Postman's Anvils in America has an 1899 ad that descibes 5 sizes of these vises and Fisher labeled them #2 through #6, with #6 being the largest-- 8" jaws, 10" opening, and weighing 160-lbs. I have an early #2 size and the ad states that that vise weighs 65-lbs and came with 4-1/2" jaws. No leg was configured for the #2, as it was supposed to bolt right to a bench or work station, I suppose.This vise was found in Trenton, NJ about 10 years ago and has probably never traveled more that 12 miles from where it was made. Pictured with it is a No. 2 Stanley plane for size comparison.
I also own most of a #5. It's missing the lower screw, the gear, and the chain. Clark Fisher received a patent for this vise design in 1883 and was issued patent number 282975.