Quick FYI for the bench-techs in the group.
A few months back, I became aware of this device, as well as the others
produced by the same fellow:
http://www.voltagestandard.com/DMMCheck_Plus.html
He's producing several types of low-cost, precision voltage / current /
frequency references. Prices are reasonable, especially when you consider
the re-cal program.
Any of these should be more than adequate for the vast majority of our
reference / cal requirements.
(I have no connection to the mfr. But I do like the product, and wanted to
pass it along.)