HC, HHC, I got my dating certificate at last and and it's '62 S'procket exported to usa then back via Germany, (long story) However the c/ case has just got an H stamped on it. Wonder if it means not much compression!!
I have heard that on occasion the apprentice was let loose to stamp the cases and on a post on another forum the lack of or miss matching of numbers was discussed , wrong size font and double punched have been seen.
As I understood it HC equated to 8.5 to 1 and HHC anything above. Plus the different cams.
But there are here more knowledgable than I.
Cheers