RSM (Radiac Survey Meter) No. 2
The British 'Radiac Survey Meter No 2' dates from 1953-6, and required obsolete 15 and 30 volt high voltage batteries in addition to a 1.5 volt standard cell (which powers the valve heaters and light bulb). There was also a training unit which measured 0-300 mR, and ran on four 30V cells plus one 1.5V for the filaments. This meter used a large GM tube as opposed to the ion chamber of the RSM No 2.
These meters were favoured as they had been tested on fallout in Australia after Operation Buffalo nuclear tests, and were retained until 1982 by commissioning a manufacturer to regularly produce special production runs of the obsolete batteries.
The UK's Royal Observer Corps initially used the RSM No 2 as its prime radiation detector until it was replaced by the specially designed 'Fixed Survey Meter' which used the same obsolete high voltage batteries as the RSM. The ROC retained the RSM No 2 for use during external 'post attack' mobile monitoring surveys.

The Radiac Survey Meter No.1

This was slightly bigger in size and had a fixed handle compared to the RSM No.2.
It was a trainer unit, used to teach the use of the RSM No.2 and had a detection abilty that was very weak, weak enough to pick up the training sources used to simulate Radioactive fallout.

Will post up my pictures of these tommorow.