Stephens Patent Vise Co.
The Trow City's Directory in 1879 announces the incorporation of the Stephens Patent Vise Co. President: Nathan Stephens, SEC: Benjamin F. Stephens - $10,000 capital
Despite the above announcement, we find the company listed in the Centenial International Exhibition in 1876.
I do find references to a patent for a vise in 1842, and an improvement in 1845. I've yet to find those patents.
In the 1882 edition of the Hartford City Directory, we find the advertisement for Asa S. Cook claiming they are the manufacturer for the Stephens patent vise. (See Image below)
1882 Hartford, CT City Directory Advertisement