If I had to guess, I would say post-WWII German production, possibly imported by any number of different companies.
NOT Steelcraft... their 1952 catalog shows their adjustable wrenches as having "fully polished heads, royal blue handles".
Steelcraft's 1961 catalog shows a 6 inch and an 8 inch adjustable with "red enamel handle", but they do not offer a 10 inch size in that series.
I don't have any catalogs for Oxwall that go that far back, but that is a possibility.
Also might be from Japan, but the head thickness causes me to lean more to "German".