The 400 GL have the most sensitive ranges of 0.1 mV (100 µV) full scale. The “L” indicates the presence or emphasis of the log scale on the display. These meters also have amplified AC V output terminals and can be used as preamps for a digital scope, less sensitive AC voltmeter, or a chart recorder with an AC voltage range. They also have front panel switch selectable 100 kHz filters.
Unit powers on however no further evaluation was performed. Exact unit pictured is for sale. Shows cosmetic blemishes (seen in photos).