lot of slide rule manuals instruction books, Post Versalog, K&E Polyphase Duplex, Aristo Studio

Lot of three vintage manuals for the old slide rules as shown, all in good used condition.

Keuffel and Esser Polyphase Duplex 4071, book dated 1939

Fredrick Post Versalog, book dated 1951

Aristo Studio - I didn't see a date on this one, mid century.