Originally Posted by Aubergine

The reason we think it has been hacked off is that the old Simplex derailleur hangers were not compatible with other derailleur brands such as the Campy on your bike. People thus cut them off and used a bolt on ("claw") derailleur hanger. Also, behind the claw you can see the abrupt change on the frame's dropout from rounded at the rear to flat at the bottom.



Both steel wool and a derusting agent (a mild acid) will clean that frame without damaging it.

EDIT: I've just peered at the rear dropouts on the OP's first photo above, and it appears that the non drive side dropout has the same shape as the drive side dropout. In other words, it has the same abrupt transition from curved to flat. Let's see some better pics.

Also, is there any sign of chrome on the front fork?