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ounce

1

Various units of mass in the English-speaking world, 15ᵗʰ – 20ᵗʰ century. The most common is the avoirdupois ounce, ¹⁄₁₆th of the avoirdupois pound, approximately 28.3495 grams.

The apothecaries' ounce and the troy ounce, ¹⁄₁₂th of the apothecaries' pound and the troy pound respectively, have identical masses, approximately 31.1035 grams.

2

In the United Kingdom and United States, ? – 20ᵗʰ century, a unit of thickness used in grading thin, flexible leathers. One ounce = ¹⁄₆₄ inch.

sources

3.2.146. Ounce. A term used to indicate weight or substance of certain kinds of leather (such as upholstery, bag, and case leather). In theory it is based upon the assumption that one square foot of leather will weigh a certain number of ounces and will uniformly be of a certain thickness; hence, a three-ounce leather theoretically would be one square foot of leather weighing three ounces. In practice, this varies because of specific gravity of tanning materials used and for that reason a splitter’s gauge has been adopted which controls the commercial thickness of leather when sold by the square foot. An ounce is equivalent in thickness to ¹⁄₆₄ inch = 0.0156 inch = 15.6 mils = 0.4 millimeters.

Federal Test Method Standard.
Leather, Methods of Sampling and Testing.
Federal Test Method Standard No. 311 (January 15, 1969).
Washington, D.C.: General Services Administration.
Section 3, definition 3.2.146. (Document is loose-leaf.)

3

In west Cornwall, 19ᵗʰ century, a researcher recorded “ounce, the sixteenth part of an property”. It's interesting that within the space of a few centuries (since the advent of avoirdupois weight) one meaning of the name of the unit could be its numerical relationship to the larger unit, completely losing its dimensional meaning. A replay of uncia to inch and ounce.

M. A. Courtney.
West Cornwall.
in Glossary of Words in Use in Cornwall.
Published for the English Dialect Society.
London: Trübner and Company, 1880.