The image below is an Ellipse Guide. But what is an ellipse guide?
Before Illustrator it was near impossible to draw a 43 1/2 degree ellipse but these handy guides got you close.
I have a vast array of various guides just waiting in storage for the day the electricity is forever gone. (Link)
Visit the online museum to see the Haberule Type Gauge, drafting brushes, a Specialty compass and other forgotten art supplies. You can also submit images of any artistic tools, machinery, gadgets, etc. that you feel have bitten the dust.