This is a Model 287 charger-reader manufactured by the Victoreen Instrument Company of Cleveland Ohio. Quoting a 1947 product description “The Minometer has been designed to measure stray radiation as well as extremely small X-ray and gamma ray quantities. The instrument consists essentially of a string electrometer and a small ionization chamber designed in the shape of a fountain pen for carrying in the coat pocket. The value of the ionization chamber, as well as the scale supplied with the instrument, is 0.2 R which is twice the accepted quantity estimated for a daily tolerance dose.”
The exposure (in mR) was determined by measuring the decrease in charge in the condenser chamber as a result of the radiation exposure. The condenser chambers that the Minometer charged and read were used for personnel monitoring. Because the exposure could not be determined without the Minometer, the chambers were referred to as indirect reading pocket dosimeters.
The box at the base of the instrument measures 14 cm by 8 cm. Various models of dosimeters appear to have been used. The Victoreen 754 in the last two photographs measured 9 cm in length. The fifth photo shows the reading as seen through the viewing tube that projects up from the rectangular base.
