John,

I am betting on Diamant. I have an RV-3 canopy in my garage, and it looks nothing like that. RV-3 canopy is blown bubble, with sort of a teardrop shape when viewed from above. Side view of the RV canopy, rises rapidly at one end, long, slow taper off to the pointier end. This looks to go up from the rounded end, then go closer to flat.

If the window cutout is level with the bottom, it is a Diamant canopy. If it is at a noticeable angle, it is likely an ASW-12 canopy.

P-51 canopy would be MUCH thicker, and would have flats with near 90 degree corners at the "open" end.

Steve Leonard