MLA

Plowden, David (1932). Central Vermont Railway, Extra 468 North Meets Extra 472 South. Amherst, Massachusetts (No number extant). Box 175. circa 1954. https://collections.library.yale.edu/catalog/10593382.

APA, 6th edition

Plowden, David (1932). (["Box 175"])(circa 1954)[Central Vermont Railway, Extra 468 North Meets Extra 472 South. Amherst, Massachusetts (No number extant)]. https://collections.library.yale.edu/catalog/10593382.