UPDATE

I found the man and he gave me 5 more addresses with PK like the one in the txt file, all around 0.5-1.1 btc on it.
He has also about 10 of them, and tell me how pap and he get this from a other friend that was a computer programer (and dont ask, the man dies some years ago ).
And they have use 3 in 2015 or 2016 or 2017 to go on a fishing trip.

He is a bit dementia and cant remember how they make the bitcoins to money, but all happend on a pc with a Bitcoin Core software he had ( yes he "had" but his son put a new SSD in with windows 10, old was broken)

So when i told him about what i found and what bitcoin is gona be, he walk to a cabinet and gave me a paper and all the keys are on it written by hand.

The sad thing is he talks with me and stops and then ask, who are you ... all repeating, i was happy his son was with me and handle the situation real good.

At the end he gave his son the keys he forgot, he has, and now we both have this 53 char long PKs.

What i figure out with all the PK i saw is

53 Characters
hex format
no big I or big O letters

and thats it. Somebody a idea ??