a plate perforated with rows of different numbers of equally spaced holes as a guide for indexing work.
Origin of index plate
First recorded in 1815–25
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for index plate
Historical Examples of index plate
This fuze is opened at the required number of seconds, by cutting close to the right of the mark on the index-plate.Ordnance Instructions for the United States Navy.
Bureau of Ordnance, USN