those with some types of brakes had to have that manufacturer's fluid and others the opposite, such as Dunlop fluid only in Dunlop systems and Girling fluid only in Girling systems, because of chemical incompatibilities between different types of seals and fluids. I know for sure that my old Lancia Fulvia Coupe had Dunlops and my '66 Maserati Quattroporte had Girlings and there were emphatic warnings in both manuals not only about the brand, but which COLOR of fluid from that brand's several offerings. So maybe the crystals are the result of combining incompatible fluids, even adding the current universal DOT type to older stuff.

I assume that a new set of rubber parts in a rebuild kit (if it's really new and not New Old Stock from 30 years on the shelf) will be compatible with current fluids.

Is this one of those Daimlers with the lovely little 2.5 Hemi V8? -- I knew a fellow with an SP-250 in Minnesota in the '60s.