Thanks Blain

I thought that it had to be a RC value. But I am still a little confused. RC 47 equates to BHN of about 444. Multiply by the rule of thumb 500 to give PSI tensile then we are well over 200,000 PSI so that is great.
I would however be a little concerned with the brittelness of plain 0.4%C steel at that hardness. Is it a core value or a additionaly surface carburised value ?

Regards