Besides being a cool uncommon tool to own, it's also a key knowledge base tool.
With the PLVMB marking, the MFD. marking and the herringbone pattern grip, it could only have been made in the former J.P. Danielson factory from November 1946, after the Plomb Tool Co purchase, through December 1948, before Plomb embarked on the doomed Dual-Marked debacle in January 1949, and certainly no later than March 1950, when all traces of their company name were removed from the tools.
That jibes perfectly, and vice versa, with the series of wartime and immediate postwar catalogs and my dating analysis of them...
The No. 203 bent nose pliers first appear on page 62 of Catalog 19-R THIRD PRINTING, which also features (also for the first time) a J.P. Danielson adjustable wrench (instead of a Utica). I date this catalog to NET 10/1946 to NLT 3/1948. Note that it does
not appear in any catalogs prior to that. It appears again on page 62 of Catalog 19-R FOURTH PRINTING, and then on page 35 of the first Plomb Tool Co. catalog to feature Proto branding, Catalog No. 4820.
You can see a handy chart and my rationale in a post in the Plomb Lawsuit thread linked
here.
On a side-note, I have always admired the pliers in this era. I have had a few and although they were not as vivid in survival as their depiction in the catalogs, they are handsome tools, sporting a two-tone finish, with the head being "polished" and the handles being much darker, almost black, what Plomb called "gun metal" (assuming Parkerized or Sheradized), with a stark diagonal dividing line around the pivot area.