Lynn, it's the old British system BS970, superseded some years ago by a newer version with different codes.
Freecutting MS that you mentioned was EN1A and is now 230M07 where the 07 indicates carbon content, i.e 0.07 %. EN8 is now 080M40 so 0.4%. Carbon content is a good indicator of a steels ability to be hardened.
EN40B is now 722M24 and is a 3% chromium molydenum nitriding steel that when nitrogen hardened (nitriding) has a very hard wear resistant case and a tough (60tons) core. Ideal for a crank!
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Adrian Barrell
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