John Rabone & Sons, folding rule, Boiler makers

John Rabone and Sons, Birmingham made folding rules.

Some were particularly specialised. This one maybe a boilermakers rule (scale for copper furnaces)

This is labelled
"John Rabone & Sons Birmingham"

It is not numbered.
It does however have some unusual scales

1)  Copper Furnaces
Top, Sides, LTC B, Galls

2) Flat Iron
per Foot
by 1/4in Thick
Also Square iron per foot

3) Round
     Iron
per foot

4) CWT

Has sliding vernier measuring in inches