Hi Luckystrike
It seems to me, to be a part of a sight "hatch" from a Stug III. This sight was placed in front of the commanders cupola and its hatch had a rectangular opening with rails to slide its cover. Basically, what you got there is part of the roof from a StuG III, most likely a G model. Sorry for the crappy description, english is not my primary language.
Best regards
Pablo
Bookmarks