Thanks all for your feedback.
Bill, despite VERY diligent questions and search I haven't been able to find out who did the stocking, finishing, checkering and the metal finishes.
Weight is 8^7. My friend Craig Libhart of Susquehanna Stockworks has identified the wood as American Black Walnut. He suggested I remove the pad to look for a stocker's cartouche but I haven't done that as yet. Sorry, that's all I know except that she's been hunted a little since restoration and will absolutely turn clays into smokeballs.
Drew et al., the 3-inch/1-5/8 ounce progressive loading was intro'd in about 1935 along with the Winchester Model 12 Heavy Duck pump gun, and again, there are significant differences in the borings of this 1941 Wild Fowl as compared with my 1927 LCS Long Range that was made for the 3-inch/1-3/8 ounce load. More to come as I make time to compare the two
special long range Smiths against 3-inch Super-Foxes and Winchester Heavy Duck Model 12's and 21. That will be objective testing with 3-5 shot composites and with ducking size shot for pattern efficiencies
and penetration at 40-50-60 and perhaps 70 yards depending on results obtained.