While browsing the scan of the 1953 Radios Master from w140.com (many thanks!), I stumbled across the advertisements placed by Measurements Corporation. I was surprised to see they had two VTVMs in their product line: the Model 62 AC/DC VTVM, and the Model 67 Peak-to-peak AC VTVM.
They are in cabinets styled similarly to the Model 59 Megacycle Meter (grid-dip meter).
(Photo credit: Western Historic Radio Museum)
The Model 62 has a vacuum tube RF probe and an unusual pushbutton range switch.
I have a Model 62 on its way, but of course without the external RF probe.
I managed to find one good photo of the probe. Does anyone have photos of the probe from other angles? I’d like to try to reproduce it.
John F. Rider’s book Vacuum-Tube Voltmeters, 2nd edition, 1951 has schematics for both the Model 62 and the Model 67. Pete Millet has a scan of the book on his excellent tubebooks.org site, and I’ve excerpted the schematics from that scan below.
Model 62 VTVM
Model 67 AC VTVM
My Model 62 arrived.
Update:
I happened upon an article in the September 1943 issue of Radio News on the American Radio History web site. In it, McMurdo Silver describes his "Laboratory Type VTVM". Take a look at the photo accompanying the article:
It looks familiar, doesn’t it? The circuit is essentially identical to the Measurements Model 62.
McMurdo writes as if the diode tube in the RF probe was an innovation. Was this the first VTVM with a vacuum tube RF probe?
It looks like a commercial product, although the article doesn’t mention that. The plate on top says “Fada Radio and Electric Co., Inc.”
I made an excerpt of the article, available here.