This specimen is a Langdon No. 1124 from 1968. The smaller size (18″ L x 4″ D work table), perforated one-piece cast iron frame and no provision for length/work stops are its distinguishing traits. Like most of the late production miter boxes it shares many interchangeable parts with the various other models. We have seen another one dated 1955 that is identical to the one shown below in every respect.
Compare this also to the Proto 931 of the same era, which is also identical.
Photos courtesy of Adam Agnello.
A Langdon Mitre Box Reference 