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A. W. Faber Castell Addiator Darmstadt 1/54A

• Type: Closed Body Darmstadt
• Size: 11 Inches / 27 cm
• Material: Mahogany and celluloid, reinforced with brass fillets
• Scales:
  • Front: cm L / K A [ B CI C ] D P | S T
  • Back: [ LL1 LL2 LL3 ] Addiator built into frame
• HvH: 883

The 1/54 is the canonical Darmstadt rule, and one of the most popular in Faber's catalogue. Almost identical is the variant model 1/54A. The 1/54A would be confused with the 1/54 until the user flipped it over. Boy Howdy, ladies and gentlemen (er, that is, meine Damen und Herren ), this slide rule can add and subtract. Faber embedded an Addiator into the frame. Careful analysis suggests this is an actual off-the-shelf Addiator with an extended-length clearing handle long enough to reach the right-hand end of the rule. A brass and hard rubber stylus is stored in the left-hand end.

In green paperboard case. Cursor has a crack preventing it gripping the rule; its tension spring is also missing. Perhaps surprisingly, the Addiator stylus is present. Dated about 1945, based on cursor style. (Even if the cursor isn't contemporary, the rule would likely have been made before the founding of the Federal Republic of Germany in 1949 (based on the "patent pending" notation "D.R.P." [Deutsche Reichspatent] in the groove of the body).