German Heeresmeldenetz / Quadratmeldenetz on 1:50,000 maps - how to read or extend the grid?

[WiseFinder]

Hello everyone,

I have a question about German wartime map reference grids used in the Leningrad region in 1943. I am working with a German 1:50,000 map:

Rußland 1:50 000, Lopuchinka, Blatt O-35-11-D, Ausgabe V.1943

The map has an orange/red overprinted reference grid. On the sheet I can see large lettered squares such as WV, XV, YV, etc. The rows seem to keep the same second letter, for example the "V" row continues horizontally, while the first letter changes from west to east. The grid also seems to use the familiar subdivision pattern: large square → number 1-9 → lowercase letter a/b/c/d.

For example, if I take a reference such as:

XV 6 a

my understanding is that:

• XV is the large reference square;
• 6 is one of the nine subdivisions inside it;
• a is one of the four smaller subdivisions inside that;
• so the result should define a relatively small square on the ground, probably around 1 × 1 km if this is the usual Heeresmeldenetz / Quadratmeldenetz system.

I am trying to understand how this system should be handled correctly.

My questions are:

1. Is this overprinted system on the 1:50,000 German maps best described as Heeresmeldenetz, Quadratmeldenetz, or Orangemeldenetz?
2. Is the large two-letter square normally 6 × 6 km, with the next digit giving a 2 × 2 km square and the lowercase letter giving a 1 × 1 km square?
3. If a point of interest lies just outside the available sheet, is it methodologically valid to continue the visible grid lines into the neighbouring area, assuming the sheet is correctly georeferenced?
4. Were the letter designations consistent between neighbouring sheets and different scales, or could another overprint / Zusatzzahl use the same physical grid but different letter labels?
5. Is there any known converter, table, manual, or explanation for this specific German army reference grid system? I am not looking for the Luftwaffe Gradnetz / Jägermeldenetz converters, but specifically for this kind of army map grid with references like XV 6 a.
6. If a wartime source gives a reference in a form like two capital letters + number + lowercase letter + possibly one or two final digits, how should the final one or two digits normally be interpreted?

I am attaching the Lopuchinka 1:50,000 map as an example, because it clearly shows the grid and the lettered squares. I am not asking anyone to identify a crash site or a unit position; this is mainly a technical question about how to read and extend this German map reference system correctly.

Any help, examples from other German maps, or references to manuals would be greatly appreciated.

Thank you!