BASIC DESCRIPTION Antique Addometer portable mechanical adding machine #4 by Reliable Typewriter & Adding Machine Company, Chicago, Illinois. Stylus-operated dial adder, vintage calculator, antique office machine, 1927–1950s hard-shell leatherette case with purple velvet interior. Fully functional, cleaned and oiled. Distinctive faceplate with full operating instructions printed directly on face. Two-piece original documentation: illustrated Directions fold-out with Guarantee section and Caution operating card from Business Machine Service.
FULL DESCRIPTION
Some Addometers are remarkable for their papers. This one earns its place on the faceplate alone.
What You Are Getting
A fully functional antique Addometer portable mechanical adding machine by the Reliable Typewriter & Adding Machine Company of Chicago, Illinois, in its original hard-shell leatherette case with purple velvet interior. Stylus included. This unit features a distinctive faceplate variant with complete operating instructions printed directly on the face — "(+) To Add — Use Large Figures — Turn to Right / (-) To Subtract — Use Small Figures — Turn to Left" — with STYLUS and CLEARING LEVER positions labeled. A self-contained instrument that needed no separate instruction sheet to operate.
Documentation included:
A Note on the Faceplate
The printed operating instructions on the faceplate represent an earlier or alternate production variant — the machine was designed to be operable without consulting a separate document. Combined with the ADDOMETER TRADE MARK designation and the full guarantee text on the accompanying Directions sheet, this unit has a character distinct from the others in this collection.
A Note on the Case
The hard-shell leatherette case with purple velvet interior and gold embossed ADDOMETER nameplate is the premium production variant from Reliable's primary manufacturing run at 303 West Monroe Street, Chicago: 1927 through the late 1950s. Distinct from the later cardboard-box editions. This case shows more significant age wear than others in this collection — honest patina from decades of use, not damage — and the machine inside is fully operational.
How It Works
The Addometer is a stylus-operated mechanical adding machine — a dial adder — introduced in 1927 by the Reliable Typewriter & Adding Machine Company of Chicago. Insert the stylus beside a large inner digit and rotate clockwise to add. Use the small outer digits and rotate counter-clockwise to subtract. Results accumulate in the windows. Pull the zero lever to clear. No batteries, no electricity — precision mechanical arithmetic that has worked for a century and will work for another.
From the STEMpunkED Collection
This piece comes from STEMpunkED, a hands-on educational initiative dedicated to teaching science and computation through the actual instruments of history. More pieces from the STEMpunkED collection will be listed over time. Please see other listings.
CONDITION Fully functional — all dials, clearing lever, and stylus confirmed working after individual cleaning and oiling. Original hard-shell leatherette case with purple velvet interior intact; exterior shows more pronounced age wear than others in this collection including edge wear and corner softening, consistent with heavier period use — honest patina, not damage. Both original documents present with expected age toning; Directions fold-out shows light handling wear.
Returns: 30 days. Buyer pays return shipping. Shipping: Buyer pays shipping and insurance.