Hi Chris.....this is a Haenel, but the sight design is along the same lines;

http://www.flickr.com/photos/3122848...7624218336819/

There was on yours a strip of metal with the back bent up at 90 degrees (this is where the sighting vee was)....it had a depression in line with the bar in your sight base to position it, (it fitted under the bar) and a little spring at the front to push it up....there was a sliding bar on the strip to adjust the elevation....unfortunately these are often missing on these mark 1's, but they do turn up either secondhand or on fleabay from time to time.....my memory is playing me up, but I think your "tray" has a dovetail, and if so you can knock out the "tray" and a BSA rimmy rear sight will fit...I may be wrong and if so hopefully some can correct this. Now these rimmy sights are common, and you could look at fleabay number;

150463736530

The scope mounts as you say are a different size, but I am also sure I have read on here that someone makes something?