Accession No

3049

Brief Description

flank observation calculator, attributed to J. H. Steward, English, 1/2 20th Century

Origin

England; London [attributed]

Maker

J. H. Steward [attributed]

Class

calculating; military

Earliest Date

1900

Latest Date

1950

Inscription Date

Material

plastic (two types of celluloid); metal (brass); rope (string); thread (synthetic)

Dimensions

length 198mm; width 117mm

Special Collection

Steward collection

Provenance

Collection purchased from member of the Steward family, 1974.

Inscription

Description Notes

Funnel-shaped sheet of transparent celluloid with central vertical slit which allows movement up and down shaft of back T-shaped panel (also with slit and capable of motion), and relative to disc held at fulcrum.
Front sheet has degree scale at top marked ‘observation’, divided 4˚ - [0] - 4˚, numbered by 1˚, subdivided to 10´. Scale along slit for ‘range O.T. in thousands of yards’, divided [500] - 10[000], numbered by 1[000], subdivided to 500. Conversion table between feet and metres. Piece of synthetic thread attached at bottom.
On central disc: degree scale divided 100˚ - [0] - 100˚, numbered by 10˚, subdivided to 5˚. Inscription reading ‘radius of circle on brass stud = 50 yards. Diametrical scale divided 400 - [0] - 400, numbered by 100, subdivided to 50.
Back panel: degree scale at top, marked ‘battery range & line’, divided 3˚ - [0] - 3˚, numbered by 1˚, subdivided to 10´. Scale along central slit divided 0 - 10000, numbered by 1000, subdivided to 500. Piece of string attached at bottom .
The three parts can be kept from movement relative to each other by tightening knurled brass screw.

Condition fair (hole in front panel); complete

References

Events