After the shift on 23 December the miners of the Erzgebirge celebrated in their mines the Mettenschicht. Still today many christmas hootenannys take place underground in former mines. For me they are among the most beautiful. Our miner is facing the following puzzle:
The letters A, B, C and D represent four minerals that are hidden in a gallery. Write the letters A, B, C and D) in some fields of the grid. Each letter must occur in each row and each column exactly once. The remaining fields are blank. Letters outside the diagram indicate which letter you see if you look into the grid from that point. Numbers in the grid indicate how many letters are on the 8 neighboring cells. Cells marked with a number are empty.