Pilot,
This is the only E-3 canopy I know; that is "earlier" style canopy.
The "late" canopy being use on E-3s, too (See WNF production) however.
As for your frame, I understand what you mean, but chose a better angle of view to be sure that your E-7 frame is at the position you pretend to see it.
As it is said:
We don't know with that WNr. - through known production batch - if it is an E-4/B or an E-7 for sure (as the plane is in flight we cannot see the bigger oïl tank!
))
To be correct we don't know - without WNr. - how to make the difference between an E-3 and an E-4 when both have the "late" style canopy.
In fact, still to be precise - there is a way but we need a sharp photo displaying the lettering on underwing MG/FF fairing which is present only on E-4. (refer to Le Fanatique de l'aviation "Le Bf 109 dans tous ses états"... and to some past eBay pictures (two, only!))
And to make things easier White 21 has no armoured plate when my JG 2 E-3 extract has!
Best regards, Franck.