This portable scintillation ratemeter is a model 1413A designed by the Atomic Energy Research Establishment in Harwell, and built by Isotope Developments Ltd in Aldermaston, between 1946 and 1958. This ratemeter was modified for the specific purpose of performing geological surveying. The scintillation ratemeter is kept in a portable black leather case which can be unbuttoned to uncover different sections and panels of the ratemeter. The ratemeter itself has a wooden casing with an ammeter glass dial on the top (which can also be seen through the case via a cut-out in the leather casing). The wooden casing has its own plastic handle, and in the centre of the casing are the switches which turn on and adjust the ratemeter, as well as the jack for the ratemeter’s headphones. The casing also has this ratemeter’s serial number: No A 120. The side of the casing has a screwable cap where the mercury battery cells are replaced. This portable scintillation ratemeter 1946-1958