Keeping it cool: A rare manual for butcher shop refrigeration (c. 1938)

Albert Einstein is, of course, best remembered as one of the inventors of an absorption refrigerator known as the Einstein–Szilard refrigerator (1926). That model never caught on, but the kind described in the present unrecorded manual likely did.

Illustrated throughout, the 60-page manual explains the mechanics of small cooling machines and offers practical advice for keeping meat fresh—essential knowledge for any pre-war butcher. It  includes detailed diagrams, photos and operational instructions.

As the title-page notes, this is the second edition. This appears to be the only copy extant of any edition. A fascinating look at applied refrigeration history in the meat trade.