You are on the ball! That is what I think I am going to call the Cache..
Some info I have dug up:
This was a movie featuring the crew of a U-96 a top Tonnage German Sub movie came out in 1981
It cost 18.5 million dollars, one of the most expensive films in the history of German films.
Boot means 'Boat' in German, Wanderschuh means Hiking Boot.
I will figure something out for the listing.