In late 1941, the Wilton Tool Corp. offered their first and only vise at the time, the 4" machinist model.
From 1942-1943, the Wilton Tool Corp. started offering many other vise sizes, including the 4" HD and 4-1/2" HD models.
While, the Wilton Tool Corp. did sell it's vises directly to the general public at that time, it needed the HD models in order to meet the US Governments GGG-V-436a requirements for their 4" and 4-1/2" vises to be sold to the military. This is the reason Wilton had -2- different models for the 4" and 4-1/2" machinist vises at that time.
They also made a 3" HD model briefly, although both the std. and HD of that size were GGG-V-436a qualified.
The Wilton C1 combination vise was first introduced in 1945 and was also GGG-V-436a qualified. The "C" series vises were never categorized as HD.
Wilton continued to sell the standard 4" and 4-1/2" machinist vises until 1953 as their "Export" model.
However, in 1954, Wilton eliminated the lighter duty machinist vises and changed the machinist vise models to what is still used today.
