C-97A PIE FACE (the very first BIG SAFARI program) was assigned to Det.1, 7405.SS at Rhein-Main.
The bulbed porthole was an observer station (one on each side). PHOTINT including the BIG BERTHA 240" (6100mm) camera. 
Due to altitude limitation inside the Berlin Corridors, C-97A 49-2592 flew most of its missions along the
eastern borders where the full potential of the 240" lens could be used from a higher altitude.
Templehof, June 1960.
<br /><br />
<small>The Big Safari program name mentioned corresponds to the period when 
the aircraft was photographed. The aircraft modifications and the Big Safari 
program in which this particular aircraft was involved were not necessarily 
the same before or after.</small>