Mono slide

Monday morning and the weather is not playing ball so what better time than to tackle the eBay pile, which has accrued in the last six weeks of The Clearances.
This wee gem has been saved for another day as feeling less ruthless. It’s my grandfather’s slide rule, nope I don’t know how it works either but as a maths geek, love the equations on the back and think they might help with middle son’s advanced maths  Higher this year... ‘cot ’ and ‘cosh’ I had totally forgotten the existence of but there’s a faint bell ringing

Which brings me to one of my most favourite jokes:

If a Mathematician gets constipation....

Does he get a slide rule to ... work it out?