English: A Swedish Mollier diagram (h-s diagram) mounted on a wooden board, estimated to be from the 1940s and used by engineers for graphical thermodynamic calculations prior to the digital era. The board measures approximately 32 × 21 × 1.5 cm and weighs 284 grams. Annotations at the bottom left read "1 Värmeenhet = 1 mm, Entropienhet = 500 mm" (1 heat unit = 1 mm, entropy unit = 500 mm). Faint remnants of text along the right edge likely spell out "Mollier" and one or two additional, but unintelligible, words.