Tom et al,
According to the _Directory of American Toolmakers_, the working dates for Herman
Boker & Co., New York City, were from about 1837 to, at least, 1969, and a fairly wide range of tools bearing several different Boker marks have been reported. The DAT also opines that the majority of their offerings were probably made in Germany (Hermann and Robert Boker came from a long established tool/cutlery making family in Solingen), but acknowledges that they may have had facilities to produce items in the U.S. as well.
Also, the DAT indicates they acquired the Valley Forge Cutlery company some time after 1900 (Valley Forge trade mark registered in 1936), used the "TREE" trade mark for knives (registered in 1949), and possibly were agents for other American firms. (The latter is verified by an entry in the 1874 _Wiley's American Iron Trade Manual ..._, and an 1873 advertisement, which clearly indicates they were agents for the Lamson & Goodnow Manufacturing Co. of Shelburn Falls, MA.) Among other items, they were also gun dealers, with civil war documents indicating their participation in supplying arms to the Union troops (40,000 guns at one time in 1861).
More to the point, an 1872 Directory listing indicates that Hermann Boker & Co. were proprietors of the Manhattan Cutlery Company and the Trenton Vise & Tool Works. The 1874 Wiley's source, spells out the latter connection in more detail:
"TRENTON VISE AND TOOL Co. - Hermann Boker & Co., 99 and 101 Duane Street, N. Y., Proprietors. J. Howard Murray, Trenton, Superintendent and Manager. This works includes iron foundry, forge with over twenty fires, machine and finishing shops and brass foundry, and manufactures vises, sledges, hammers, picks, mattocks, and miscellaneous tools, with castings, iron bridges, and turn-tables, and general foundry work, with brass, composition, and Babbitt metal castings in the brass foundry. The shops are large, well-lighted and ventilated, and conveniently situated, giving employment, when running full, to about 100 hands. Under previous owners, the Trenton Vise and Tool Co. was not successful, but since the property of Messrs. Hermann Boker & Co., and under the management of J. Howard Murray, Superintendent, it has done a profitable and increasing trade."
So, I think it a very good possibility that the vise you saw was made in the Trenton Vise and Tool Co. works. I am attaching, below, a couple of images of Hermann Boker & Co. advertisements from an 1873 source.
A vise very similar to the one you saw is listed in the Otto Young & Co. "Tool and Material Catalogue" of 1892/3. This Chicago firm specialized in supplying the watch and jewelry trades. As no specific usage is given, I think it (supplied in two sizes by Young & Co.) was for general light metal work.
Hope this helps.
Don McConnell
Eureka Springs, AR