I just located my missing 'Osram Lamps and Tubes' catalogue from January 1958. Stuck int the top of the wardrobe under 'other stuff'.
Anyway Osram BGE made a version of this called the 'Film Studio Class S'. The description reads as follows:
"For studio lighting, large spots and floods. Any burning position within 90 deg of vertical cap down "
The variants were available in a range of voltage and wattages between 750 and 5KW. They describe the base as 'medium bipost'. They list their 2KW version as GES base - the only exception. The envelope size was smaller - 150mm dia and 220mm long. The 5kW version was 203mm Diameter and 335mm long. Yet the Mazda you have is enormous. WOW.