This object is part of a collection relating to the history and development of calculating devices assembled by Assoc Professor Allan Bromley of Sydney University, comprising mathematical instruments, slide-rules, mechanical and electronic calculators, electronic analogue computers, computer components, kit computers, education computers, and associated ephemera.

Allan Bromley was a lecturer and researcher at the University of Sydney Basser Department of Computer Science from 1978 until his untimely death in August 2002. He specialised in Computer Architecture, Computer Logic and in particular the History of Computing. He was regarded as the world authority on Charles Babbage's Calculating Engines (instigating the building of the Difference Engine No.2 at the Science Museum London) and the Antikythera Mechanism and had extensive knowledge of calculators, analogue computers, logic, stereopsis, totalisators, clocks and time keeping and mechanical engineering.

J.Halden & Co., 8 Albert Sq., Manchester.

Bromley note:
Mfr: J.Halden & Co., 8 Albert Sq., Manchester.
Source: Bermondsey market, London. Date: 1981 / 2 / 20
"Circular pocket slide rule of metal construction. 2 ½ inch diameter. Two faces, each glass face acting as a cursor. Complete in soft leather pocket pouch with instruction booklet. Excellent condition."

Circular slide rule with pouch and instruction booklet, Halden Calculex calculator, duplex, metal / crystal glass / leather / paper, made by J Halden & Co, Manchester, England, 1920s

slide rule: Dims: 60 diam x 15
case: Dims: 80 x 70 20

concentric disks with milled winder

Scales:
Obverse: outer: 0 - 100, A | B (1 - 10), C split (1 - pi, pi - 10)
Reverse: A | B Reciprocal | C split Reciprocal
Bromley note:
Mfr: J.Halden & Co., 8 Albert Sq., Manchester.
Source: Bermondsey market, London. Date: 1981 / 2 / 20
"Circular pocket slide rule of metal construction. 2 ½ inch diameter. Two faces, each glass face acting as a cursor. Complete in soft leather pocket pouch with instruction booklet. Excellent condition."

Made: 1920 - 1929

2010/1/74

1920 - 1929