This T-square is like the one Vern used in the 1950's and 1960's, when it was required.
When drawing schematics Vern did use the T-square with the
Click on photo
Above he is drawing staking sheets
The Telephone Template left is still for sale in the 21st century. In 1961, Vern had a small one with just triangles and circles when drawing staking sheets as depicted in photo link above.