Two similarly-constructed, compact, pancake, Geiger-tubes. The thin entrance windows (typically mica) have been damaged and then removed to show the details of the design and construction of the high-voltage electrode in the counters. Both counters are based on a 5-cm-diameter case whose walls are 1.5 cm in height. Both Canberra-Dover and APTEC-NRC were suppliers of radiation monitoring equipment during the 1970-1990 period.
