Waist Gun window section ?

This was in two parts in a box of bits that were finds from USAAF bases in the South.

I have glued it back together and spent several hours trying to identify what it is from.

I attach three pictures that show it has two straight edges  at 10 inches x 14 inches.

It is curved so the longer edge was either at the top or bottom of the fuselage.

There are 5 bolt holes along the bottom and 4 at the side which are  for 1/4 inch bolts.

The perspex is 1/4 inch thick.

The reinforcer has a brass clip to hold something down.

 It is obviously incomplete so no part numbers.

The only window I can find that comes close is the waist gun forward section of glazing on the B17G with the K6 gun mount. The bolt holes and lengths come close.

Also this image shows that there was a cover placed over the opening – probably when sitting on a wet and windy East Coast airfield ?

http://www.384thbombgroup.com/WinJack3/wwII-kush_n_50_cal.html

Anyone confirm/deny or suggest alternatives ?

Most of the other items in the box were B17/USAAF.  Apart from a Gipsy Major cylinder.

I am not sure about a final one – that is a Rootes Blower ( lobe pump) in Bronze – it is either BOAT ( Bit of a Tractor) or maybe from the airfield sewage system.