Vintage WESTON 1968 Model 310 Form 3 Portable AC & DC WATTMETER, Excellent!

Description

For sale is a WESTON Instruments 1968 model 310 portable AC & DC wattmeter, left behind in the electronics inventory of my late father.   Dad was an active and avid HAM radio operator for 73 years, and was a radio and other electronics serviceman for much of his life.   This piece of equipment was in his test equipment cabinet, stored in a dry, smoke-free home.   Dad typically kept his working equipment separate from the items needing attention, so I am guessing that he retired this piece in good working condition.   However (much to his disappointment, I imagine), his daughter never acquired his electronics knowledge, and so I have no idea how to test this piece.   It appears that he took very good care of this wattmeter (see photos), but it is untested, and being sold as is, as found.
My husband helped me out with a bit of research on this meter.   Here's some of what he found:
The portable
Weston
Model 310 was designed to be a highly accurate, electrodynamometer wattmeter, with readings based upon the Absolute Volt and Ampere.
The unit is shielded to protect the wattmeter from the effects of external magnetic fields.   The original Form 1 design of the Model 310 originated about 1919.   The instrument offered here is a Form 3 design, certified in 1968.   The serial number is 18026.
Certification
mounted inside the cover provides setup and operational details.   Resistance measurements, temperature correction factors, and self-inductances specified in the certification (inside cover) were obtained by calibrating this Model 310 wattmeter against
Primary Standards
which were certified for the manufacturer,
Weston Instruments, Inc.,
Newark, New Jersey, USA
by the
National Bureau of Standards
.
Design reliability
is 1/4 of 1% of full scale for either AC or DC current on any frequency up to...  600 cycles/sec on the 100 volt range; or ... 1200 cycles/sec. on the 200 volt AND 500 volt ranges.
Capacities
:  with fields in series -- normal current = 2.5 amps; 5.0 amps maximum current.
with fields in multiple -- normal current = 5 amps; 10 amps maximum current.
Voltage ranges
:  100 volts -- 200 volts -- 500 volts.
Scale
:  250 watts
The solid wood
cabinet
is about 10-1/2" wide, 8" deep (not including feet and hinges), and 6" high
Perfect for electrical engineers, hobbyists, university or research labs, museums, or collectors of nice vintage equipment!
I hope that this is a piece that you would love to add to your collection, or to display on your workbench!!
Thanks for looking here!!
(radio shelves)