Found this one in more than wet conditions, but based on the info of istari I was able to take care:
Following things had to be removed because they were totally rotten & had become mouldy or rusty:
Old log book (no readable log were found), matches, pocket knife.
The old log book was replaced by a new one, and the cache became some kind of magical hood which also protects him from moisture.
In = candle
Out = TB Notnagel