I took my GMC-300 to the antique mall in Hot Springs, AR. I found two pieces of Frista dinnerware there. The GMC-300 readings were over 8000. I paid $15 for both of them. One fact to remember, the GMC-300 takes awhile to drop back to normat. I thought the whole store was radioactive. The dinnerware was made before WWII around 1938. Be careful about the radiation! Have fun Harlan, NETC.com
Yes Harlan I noticed the same phenomena after measuring hot items : the GMC-300 stay at 100 CPM a very long time after the source is removed. I don't know the reason. A solution is to stop the counter and restart. CPM will be correct.