At a mere 12 inches long, these are the smallest metallic miter boxes known. The telltale differences between the two models are the slightly larger depth of cut and unique style of depth stops on the model 15-1/2.
Model 15-1/2
This first specimen is apparently missing its depth stops.
Photos courtesy of Ben Bama, Seattle, WA.
However, if you look closely at the catalog ad at the beginning of this article, you’ll see that the depth stops are flat bars bearing two slots. Here are some closeup photos from another specimen, courtesy of Jon Hall.
Model 16-1/2
Alternatively, it is the model 16-1/2 that bears the usual L-shaped stops, as seen in the following specimen from the site author’s collection.
A Langdon Mitre Box Reference 