Without pulling my 1905 catalog; I believe I recall that catalog stating that Hunter could build a 16 gauge gun as light as 6.25 lbs; and this was long before the FW frame introduction. The R framed 16 gauge Smith guns I've seen were definitely slimmed down, smaller versions of the standard R frame; and although I haven't disassembled an example, suspect the lightest weight examples had additional frame cuts and/or drilled holes concealed under the lock-plates/by the stock head, etc. I've seen several FW frames with weight reduced in this fashion.