Can I connect this meter to 220vac?
The internal 150 k&Omega; resistor and diode suggest that it is indeed intended to be connected directly to the AC line, but the actual construction would not meet any modern safety standards!

The average value of a half-wave rectified sine wave is 0.45 times the RMS value, so at 220 Vrms, there will be about 0.66 mA flowing through the meter, which corresponds to 2/3 of full-scale on a 1-mA movement, consistent with the labeling on the face.