Cooper
Established Member
I have no idea how you would use it but the little channel reminds me of the place to rest a piece of chalk on the wooden blackboard instruments that were used in old school technical drawing rooms.
On the curved scale the numbers add up to make 90. Fibrous plasterers and masons, back in the day, used to have to do very complicated geometry and TD lessons, learning about mitres and compound angles etc. I wonder if it may have come from an old time technical college?
On the curved scale the numbers add up to make 90. Fibrous plasterers and masons, back in the day, used to have to do very complicated geometry and TD lessons, learning about mitres and compound angles etc. I wonder if it may have come from an old time technical college?
