[Mondial]

Rich, I just saw your oscillator voltage readings and they are consistent with a proper operation.

The reason that the grid voltage measures positive when measured as per the test procedure is due to the type of meters used at the time. There were no digital meters available which could read a negative voltage, just the analog type with a needle and scale.
 
In order to read a negative voltage, you reversed the test probes so that a negative voltage reads positive. 
You read a positive voltage on the scale but knew it was really negative because you reversed the test leads. So your positive reading is normal with the test leads connected as instructed in the procedure.

The oscillator grid voltage is actually negative, as you measured with your meter from pin 1 to ground. If you have -4 V
then the osc is working well, provided it is at the correct freq for the dial setting.