What is this Perspex bubble?
Few thoughts:


Label font does look British/Commonwealth in some way.
Flat bottom- unlikely to be cockpit canopy that curve down on the sides.
Not compatible with weapons- Search and Rescue aircraft?
Large curvature: Slow aircraft?




At some point I was considering the rear window of the Consolidated Catalina but it doesn't quite seem to fit the bill.



Tony Hisgett on Wikicommons/Source