1915-1916 K&E Keuffel & Esser 4000 Series Polyphase Slide Rule Pat 1900 w Sheath For Sale

Up for sale is an Antique Keuffel & Esser (K&E) Polyphase 10-Inch Slide Rule with its original leather case, dating to circa 1915–1916.

This early 20th-century drafting instrument features K&E\'s mahogany wood core faced with white celluloid, a metal framing cursor stamped \"Keuffel & Esser Co. New-York\" on the top bracket, and the prominent \"PAT. JUNE 5, 1900\" patent stamp along the bottom edge.

Key Details & Features:

• Manufacturer: Keuffel & Esser Co. (K&E), New York

• Model: Polyphase (4000 series precursor / early 4053 type)

• Patent Mark: \"PAT. JUNE 5, 1900\"

• Construction: Mahogany core with celluloid face, brass/metal cursor

• Scales: A, B, CI, C, D, T, S, and L

• Includes: Original stitched leather sheath case

• Metal Cursor Blocks (1915): The all-glass cursor with metal end blocks was introduced in K&E\'s 1915 catalog. By 1916, K&E switched those metal end blocks to plastic/celluloid. Because this rule\'s cursor has the original screwed-on metal blocks stamped Keuffel & Esser Co., it points right to the 1915–1916 window

Condition:

• Slide Rule: In remarkably solid shape for its age. The rule is straight, the slide operates smoothly, and the cursor glass and frame are fully intact. The metal cursor hardware exhibits an attractive, unpolished vintage patina.

• Leather Sheath: The body of the sheath is sound, though the small top closure flap has separated due to leather age/stitching wear.

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