The bottom two panes can be opened like shutters.
There was a curved shield which presumably helped to keep the wind whistling through the slot that the machine gun traversed.
AJ Press's monumental tome is on the P37 is probably hard to come by now and very expensive. Also entirely Polish text with photo captions duplicated in English.
This booklet is entirely Polish but has lots of photographs and plans reproduced to a high standard and it's very cheap.
www.jadarhobby.pl/wydawnictwo-zp-tbiu05-pzl-37-los-book-p-30944.html
That's better, found out how to edit the post so you can see the photos now. Notice there is a samll curved pane in front of the shutters. It is not always seen in photographs. Perhaps it hinged forward when the shutters opened? The only purpose I can think of for the shutters is that they were opened to use the bomb sight because the curved glass would cause distortions.
Colours. There is a lot of stupid hand wringing over the exact shade of Polish Khaki. Humbrol 155 is perfectly acceptable for the the so called 'late khaki' used on this aircraft. The light blue is identical to RLM 76. Photographs show the interior was painted and not aluminium. Some Polish modelers use khaki but examination of remains and artifacts show a blue grey colour was used very close to Intermediate Blue.