Crabtree rule

Crabtree rule

survey instrument

This Parallel Line Rule is a heavy-weighted object, suitable for life on flat surfaces. All of its part are made of brass, which is a sturdy and relatively inexpensive material. The rule is slightly tarnished but has no discernible damage. This would suggest it was a desk object and well taken care of.
It was made by H.S. Crabtree around 1930, and was eventually collected by famed Canadian surveyor Louis Sebert who collected older, non-technical objects for nostalgic purposes. In 2003 Sebert's wife handed the instrument to the Museum of Science and Technology in Ottawa where it has been ever since.
References:
Archive.org
https://archive.org/stream/uoftreportgov1944univ/uoftreportgov1944univ_djvu.txt
https://www.archive.org/stream/n01ontariosession65ontauoft/n01ontariosession65ontauoft_djvu.txt?keepThis=true&TB_iframe=true
MARCH 4
Smithsonian Online
https://americanhistory.si.edu/collections/search/object/nmah_690215
Individual Collections
https://www.mathsinstruments.me.uk/page39.html
Royal Museum Greenwich
https://collections.rmg.co.uk/collections/objects/42814.html

H. S. Crabtree ltd. Toronto, circa 1930

circa 1930's: made/marked by H. S. Crabtree
2003: collected by Museum of Science and Technology

Bass (all parts)
severe in appearance with distinctly shaped hinges that are most notably associated with H. Hughes & Son design from England.
heavier than an average parallel rule, about 2 lbs.

English

mathematical instrument used for drawing parallel lines on a chart or graph

2004.0015.1

Canadian survey instrument
Ontario, Canada