The PERM gamma detector provides gamma detection and isotope identification. It uses a low-cost 2 in x 4 in x 16 in NaI(Tl) crystal, enclosed in an IP67-rated housing, as the scintillation material. The crystal/photomultiplier tube (PMT) package is a commercial item supplied by St. Gobain. The design associated with the packaging of the COTS scintillator is driven by the need to provide medium-resolution (~8%) gamma spectra (30 – 3000 keV) with accurate and stable energy calibration.