Kriegsmarine Albert Nestler No.20 “Kiel” logarithmic slide rule. The protective black cardboard box was marked with type, manufacturer as well with the Waffenamt and “Eigentum der Marineschule Kiel” (Property of the Naval School of Kiel) which were also marked inside the rule with the property number 5538. Note the D.R.P. (Deutsche Reichpatent) inscription on the lid.
