Answer is: the symbol is the electromagnetic gripper
- We can see from the label on TC terminals 4 and 6 that the device is fed from a 123 V, 150 VA winding.
- The supply is rectified by VC. (Notice that the diode is pointing to an AC terminal which is incorrect so we don't know whether 10 or 12 is DC+.)
- SA3 is a polarity changing switch for YH but notice that when SA3 is to the right the device receives full current but when to the left current will be limited by R.
- As suggested in the comments this is probably the electromagnetic gipper.
- My guess is that full current is used to pick things up and that a small reverse current is used to remove any residual magnetism left in the iron core when the magnet is switched off.
The symbol is strange and probably made up by whoever drew the schematic. I think it is saying that if + is applied to 16 then it behaves as a solenoid but if + is applied to 18 it will not behave as a solenoid, hence the X.
If my thinking is correct then SA3 to the right should connect + to 16 so 10 is connected to the VC + terminal.