With thanks again for these pics to John, who says:
"Here are some pics of the Original 50E, which must have been a "base" model for the UK market. This has the simple rear sight in a dovetail similar to BSA and Webley of the period, and the single element front sight. There is no rear rail as on the a,b, or M variants."
The rifle is marked "MADE IN GERMANY", as opposed to "FOREIGN" marked on earlier examples of exported Dianas.
The Falke forum
The Vintage Diana Forum