CD V-700M
Geiger counter

On the aluminum probe there is engraved: OCD-P-108
These CDV700's were Modified, hence the M designation.
The CD V-700M is a modification of the CD V-700.  The modification is the replacement of the original G-M probe with a new probe that uses an end-window G-M tube.  The modification allows for a much better survey for contamination.  Additionally, the window is very thin and allows the G-M tube to detect alpha particles (not really, the newest messages tell us that it can't detect alpha radiation, more about this later). The window should be within 1/2 inch of the source to detect alpha radiation.  Incidently, the CD V-700M G-M counters are calibrated in counts/minute not mR/hr. The G-M tube has a much bigger volume than the 6993 G-M tube used in the original probe.

They are sold here http://www.radmeters4u.com/more.htm 
Here is their description:
These are new-in-the-box Model 6B meters that are incorporating a newly manufactured (2002) thin-end-windowed G-M tube (LND 723) encased in a new OCD-P-108 aluminum probe housing. (Sample of this thin-end-windowed G-M tube can be seen there in foreground of the photo.) They have been rigorously checked out, tested and recently calibrated here at our authorized lab. Calibration sticker affixed to the side of the unit. Three ranges allow for low level gamma radiation measurement at 0 - 0.5 mR/hr, 0 - 5.0 mR/hr and 0 - 50.0 mR/hr. Also, very sensitive alpha and beta radiation detection at the probe window screened end that would not be detectable by standard CD V-700 G-M tube setup. Ideal for decontamination duties of checking people and the inspection of food & water for radiation contamination.
Unit includes headphones, carrying strap and the original manual. Requires 4 common D-Cell batteries.
Total delivered cost is $475.00.

Here is a message from the CDV700CLUB discussion board on Yahoo. Written by John Boyle.

Here's the latest poop on the 700M's from a retired PA procurement agent for the RIM&C shops.  It's a little long, there are a couple personal lines left in, but some of the stuff's interesting.  I got this email this morning...jb

Dear Mr. Boyle,

Thank you for your email.  I'm retired, going on my twelfth year of uninterrupted stream fishing, but I still enjoy chatting about the good old days of Civil Defense. I remember Bill Young and Ken Yost well.  You're not the first to tell the story of Ken's radioactive coffee pot. I hear it kept many an uninvited guest from drinking the coffee at training meetings!

Here's the information I can give you on the CD V700M. I'll try to answer your questions in the order of appearance in your email.

Why were they made?
The common story is that the 700M's were developed for some health physics application.  Not so. The original plan was for each state instrument maintenance shop to modify six Electro Neutronics stock CD V-700's for contamination detection and swipe measurements of the cobalt-60 training sources within the shops, and several for evaluation by federal medical authorities for casualty monitoring.  Commercial instruments won out in that trial.

How many were made?
Later, more were produced and to the best of my knowledge about 1000 to 1200 total instruments were modified. None were ever distributed to local agencies, again to the best of my knowledge.  Many seem to have been pilfered from the shops.

Did EN inc. build the first M's?
No, none of the 700M's were ever actually assembled by EN inc.  All were done by RIM/C personnel by a directive issued by either DoD or OCD.

Who made the circuit boards?
I don't know who actually produced the circuit boards used in the EN modification.  We received them from OCD wrapped in, get this, toilet tissue in plain brown boxes.

...thyroid radioiodine uptake?
Oh, yes, the thyroid iodine uptake measurement.  That's the health physics misconception I mentioned above. The thyroid iodine uptake issue was settled later, and it was proven that the stock V700's were adequate for the purpose, although a FEMA note said that the M's could also be used for that purpose.  It was never included in doctrine though.

Is the CPM only meter on all 700M's?  I have one without it.
No, the 0-300 scaled meters made by Phastron were procured to be used in the M conversions, but the cost of each meter in the small quantity needed proved excessive, and only a small number of them were ever used. Most have the standard mR/CPM plastic meter movements, so your EN 700M is one of three approved conversions, and also the original.  The 0-300 meters came later. The other two are the EN <with> the 0-300 meter, and the Victoreen model 6b with added components to reduce the Geiger voltage to the Amperex tube's requirement which as I remember was about 550 volts. A few of the Victoreens also received the newer meters. Not many Victoreens were converted as I recall, perhaps 50-100 nationwide.  Although the mod was much simpler, the components were scarce and expensive at the time; some type of diode in particular.

How was the 700M calibrated?
By a waste of money!   All of the 700M conversions were calibrated with pulse generators, each of which cost more than all the M's in the shop with all mods in place. In general, the 700M is now considered to have been an expensive flop (pork barrel job?) which never made the splash its originators envisioned.

 

thanks goes to the CD V-700 club, John Boyle and Ruben Steinmann
Some information and the picture is used with permission from http://www.radmeters4u.com