I am building Dragon/Cyber-Hobby's Pz. Bef. Wg. III ausf. K (with Schwerer Plattformwagen Typ SSy) for the Command Campaign and came across this hole in the turret top. The instructions don't make any mention of it, neither for something to put into it, nor to fill it in. So, what would, could, should go there, or should it just be filled in?
Thanks, in advance for the help.

Happy Modelling, -zon
