I picked up this Wilpen DBE wrench - 15/16 x 1". I knew little of its maker when I picked it up, only that is was a USA maker. In studying it, it seems it is a Plomb wrench - the earliest of their offset double boxed end wrenches. It has a "0A" date code - which I believe is 1940.
Quoting AA:
"Early Offset Box-End Wrenches: The Wilpen Mystery
Instead of being introduced as new Plomb models, the wrenches were actually offered in 1933 under the brand name "Wilpen", with the catalog listing them as "Wilpen Chrome Molybdenum Box Wrenches". Plomb used the Wilpen name in catalogs until at least 1936, and the wrenches themselves were marked Wilpen, with no Plomb name or logo, until early to mid 1940.
The origin of the "Wilpen" name itself is a mystery, as the catalogs offered no background or explanation. It could be a place name or a person's name, but no trademark or company references to Wilpen have been found in an extensive search.
In addition to the unexpected name, the 818x wrenches were offered at extremely low prices as well, at least when compared with similar tools in the Plomb line. For example, in 1933 the model 8181 Wilpen wrench had a mechanic's net price of just $0.44, compared to $0.95 for the same-sized Plomb 1126 (old AD89) box wrench.
Finally, the Wilpen wrenches came with a bright cadmium finish, a departure from the polished steel finish favored by Plomb at the time. These differences in the name, design, price, and finish strongly suggest that the wrenches might have been made for Plomb by a contractor, but (until now) no credible connection has been made to their origin or maker.
One last factor adds to the air of mystery, which is that Wilpen-marked wrenches are somewhat hard to find, making them more difficult to study. Fortunately though we have been able to acquire several examples of the Wilpen wrenches, and will present them in the figures below."
