This picture was most probably taken during the early eighties at Werneuchen. 
N°58 had the external characteristics of a RBK model:
no cameras, a single lateral dielectric panel and and a longer dielectric nose cone. 
According to some technical documentation relative to this aircraft,
it was rolled out in May 1978, equipped with the <em>Kub-3M</em> ELINT suite.
As can be seen on the next pictures taken during the early nineties, 
it was subsequently upgraded to RBF standards.