Weston XM2 Cadmium Sulphide (CdS) Exposure Meter Model 550. 1972, Japanese manufacture.
Weston XM1 (left) and XM2 (right). The differences between the two meters is shown from the aspect of the Selenium (L) and Cadmium Sulphide (R) cells respectively. On the XM2 the invercone and its slide in position for incident light reading is displayed. Also visible is the 4-way sliding switch.