The 10M2 is a dual sensitivity magic eye tuning indicator that is directly equivalent to the UM4. The heater is designed for 100 mA heater chain service in universal sets without a mains transformer.
The UM4 dates to 1940. However, the 10M2 is not listed in the late 1940's Mazda handbooks and does appear to have been introduced in the early 1950's.
The grid voltage range for the whole deflection range is either 3.0 Volts or 20 Volts.
The envelope metalising obscures the envelope structure but the country of origin is visible.
Seen through the top of the envelope the control structures can be seen.
The wide glass tube envelope is 26 mm in diameter, and excluding the base pins is 75 mm tall.
References: Data-sheet, 3002, 1040 & 1049. Type 10M2 was first introduced in 1955. See also1955 adverts.
