[Test-Equipment] Vibrotest 218 B

[Jim Cundiff]

Hello All,
    I am new to this list so please forgive me if this has been covered. 
I just acquired the subject instrument. The label reads:

Vibrotest
U.S. Navy type B
Model 218
Ser No 2182319   Date 5-8-45
100 Megohms - 600 Volts
Associated Research, Inc.
Chicago, ILL

Stenciled on the back is:   MARS    AFA3GSW

The unit has space for two batteries. Can someone please tell me the 
voltage of the batteries and/or provide a copy of the manual? Thank you 
in advance for any help you can provide.

In His service,
Jim Cundiff KB3GFC