I have a surplus Air Force Geiger counter that I bought at a gun show, as surplus from Hill AFB in Utah. I had it properly calibrated by a nuclear plant technician. He found that that particular meter worked perfectly and was well within standards.
There also comes up a question as to whether or not DU is considered as NORM (Naturally Occurring Radioactive Material). NORM is NOT regulated, at all. If you filtered water enough to get a REM (Roetgen Equivalent Man) of radioactivity (a LOT of NORM), it is not regulated by anyone (in the US).
An example of NORM are the lantern mantles that Coleman used to make for their gas lanterns. They changed the formulation several years ago, but they used to be quite radioactive due to using the sand from a particular South American beach. The sand was radioactive enough that when concentrated into the mantle fabric it was quite radioactive. When I worked at Palo Verde Nuclear Station in Arizona, I borrowed one of the plant’s currently calibrated meters and took it to a sporting goods store in Phoenix. I asked the manager if I could take readings on his Coleman lantern mantles. He was glad to have me do so, as he had heard that they were radioactive. He had a large end-of-aisle rack full of them, from ankle height to shoulder high and as wide as a person. They were ten to twenty deep on each peg. They read, in the middle of the display, 2 mRem per hour. At commercial and DOE sites, that would require roping off the display as a “Radiation Area”. But because it was NORM (see below), nothing of any sort was required. Now, 2 mR/hr is not a hazardous level by itself. However, if ingested, it would be nasty. New mantles have Alpha, Beta and Gamma radiation. I also took a package of them while I was working at TMI (Three Mile Island) and read them to determine how much of each type was in them. I was rather taken aback. I determined that from now on, when I changed a lantern mantle, that it was o.k. to put a new one on, but wash the hands afterward. However, for a used mantle, I decided to wear disposable gloves and, very, very carefully put it into a plastic bag and seal it. And not on a windy day.
I was a Health Physicist at the Hanford Nuclear Reservation until about 10 years ago. Hanford was the place that made the bomb for Nagasaki. We were working to clean it up.