Me 109 canopy with slot at the top?!

[F19Gladiator]

Seems to be a "less well documented" part of the Bf 109. However, when studying photos of F-2 and F-4 versions I get the impression that the horizontal top roof part is divided into two parts, enabling the front part to slide under the aft and fixed perspex part. On some photos it is visible that the front part is located slightly lower that the aft part, enabling it to slide under.....
The "slot" is more likely a piece glued to the moving front perspex part enabling better grip when sliding it.

A photo of Wick in an E-4 cockpit on page 117 in "Major Helmut Wick" by Herbert Ringstetter, Motorbuch Verlag, in my opinion shows such a transparent "handle" pointing downwards, perpendicular to the top horizontal front perspex part - Visible as a "white" part contrasting against the darker metal frame.

Goran