Control rods. Riveted U.C.

[tankbarrell]

Lynn, it's the old British system BS970, superseded some years ago by a newer version with different codes.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!