I can't remember mine having a lid. The chinagraph holder and knob are the same.
Finally, an Aristo had to be purchased. Take a deep breath. £11. British Rail weekly wage then was about 9 quid - more if you were a driver.
One of SEN's students coughed up and then ran it over with his car. It's possible the car cost less than the computor.
Mine's still in Texas, somewhere. It has a leather case. Memories of putting talc behind the wheel to stop dragshun.
I needed a conversion a few nights ago. I picked up my Coop slide rule - ten bob, plus the cost of a replacement cursor. Another bob. I pulled, 1.88 ratio and then used W10's calculator. I was .00003 out. I made that up, but about that.
That rule was in my left shirt pocket until 9/11 closed our little airline. I'd bought it for City & Guilds work in 1958.
This model was always in my case, but seldom used.
ARISTO FLIGHT COMPUTER AVIAT 618