From the manufacturer’s website:

Model 44-183 Shielded Gamma Detector
Part Number: 47-3758

The Model 44-183 facilitates gamma surveys in high-background environments and in areas where elevated fields are directional. The detector design incorporates lead shielding that results in a 10:1 reduction in sensitivity from gammas entering in any direction but the bottom face.

The dynamic range is greatest with instruments equipped with DTC (Dead Time Correction) resulting in measurements of 10 μSv/h to 100 mSv/h (1mR/hr to 10 R/hr). The detector is a halogen quenched, energy-compensated GM.

The front plate and handle are constructed from aluminum. All exterior surfaces are protected by a durable, splatter-finish, beige colored paint. Reference markings on the detector housing indicate the internal position of the embedded GM tube.

Indicated Use Gamma survey
Detector Type Energy-compensated GM with lead shielding
Linear Range Without DTC*: 10 μSv/h to 20 mSv/h (1 mR/hr to 2 R/hr)
With DTC*: 10 μSv/h to 100 mSv/h (1 mR/hr to 10 R/hr)
Typical Sensitivity (137Cs) 0.17 cps per μSv/h (100 cpm per mR/hr)
Energy Response
(60 keV – 3 MeV) Within 15% of true value
Front to Back Shield Ratio 10 : 1
Typical Dead Time 50 µs
Operating Voltage 550 V (reccomended)
Input Sensitivity -30 mV ±10 mV
Connector Series “C”
Construction Aluminum and lead with painted exterior
Temperature Range -20 to 50 °C (-4 to 122 °F)
Size (H x W x L) 10.7 x 12.2 x 12.7 cm (4.2 x 4.8 x 5.0 in.)
Weight 3.3 kg (7.3 lb)