The early Record 'unbreakable' vices like the 110 & 112 were made of cast steel but they switched to using 'SG iron' which was a more ductile cast iron less likely to break, used on the 34 series vices.
A way of knowing if it is cast steel is the finish on the casting, steel doesn't cast nicely & needs more finishing. Look inside the vice under the static jaw, if it's steel the metal will be a lot thinner than a cast iron vice & the finish will be rougher. On my 111 steel record the metal is very thin on the non structural parts.
As far as I know Paramo & Record were closely linked, their vices were nearly identical so I would imagine that they used similar materials.
One story I heard was that Record were unhappy about being told by the wartime government to help Paramo make vices!
Thanks for the advice about identifying the material. Here is a pic of the static jaw from when I first started restoring it: