Map Refs used in Casualty Enquiry Investigation Reports?

[rlapes]

Dear Forum
Can anyone help me decipher the map references used in some Casualty Enquiry Investigation Reports dated 1946 & 1947?

In a 1947 report relating to the loss of Lancaster LM422 the following map references are used:

Place of crash: Morschied Map Ref: K50/l6932
Place of burial: Morshied Cem. Map Ref: K50/L 682322

The a/c was flying from the direction of Frankfurt K 50/660700 to Kempfeld K 50/l643328.

In a 1946 report relating to the loss of Lancaster ND645 the following map references were used:

Place of crash: Schiffenberg Map Ref: G.6918
Place of burial: Giessen Main.G.6621

In a 1947 report about Lancaster JB563 the following map references are used:

Position of crash: Bergen-Enkheim Map Ref: L51/M7373

How do I convert these references into Lat & Long?

It looks as though:
The initial letter gives the Longitude i.e. K is further West than L.
The initial two digits gives the Latitude i.e. 51 is further North than 50.
Then final part is a four or six digit reference within the grid defined by the initial letters.
It doesn't seem to fit the Cassini Modified British System of coordinates for the Nord du Guerre Zone (Germany).

Can anyone help

Thanks
Robert