Just before the New Year, my child inserted a sheet of paper with a paper wallet from my desk into the shredder. The shredder was plugged in and started shredding the sheet. I managed to pull it out, but some of the private key symbols were destroyed. In my paper wallet, I have 2 addresses with a balance:
1GkL2vdtkStT5Wa4YG1pN3f9w2P6WJQyqJ balance 43.8 BTC (41 WIF symbols survived)
1PkM3Hgw7xDrBeGWhs2zdNXSmam2BikAKX balance 5.5 BTC (31 WIF symbols survived)

There was less than a week left until the New Year and I started studying GPU software for recovering unknown characters at the end of a private key.
I decided to start with the address 1GkL2vdtkStT5Wa4YG1pN3f9w2P6WJQyqJ, where 41 characters are known.
WifSolverCuda could not solve the problem. It only recovers characters in the middle and beginning of a private key.
FinderOuter refused to start on my computer, there is only Linux (I have Windows).
BTCRecover seems to be able to recover WIF, but I could not figure out how to do it.
BITCOIN-WIF-Recovery can solve this problem, but the search time was very long.
I realized that I need to search through HEX keys.
Knowing the first 41 characters of the key, I calculated the WIF ranges
5J*9611114bdqKK
5J*9711115thGTG
The WIF keys are in sequential order relative to the private keys. I was able to determine the HEX ranges.
188****249bceb92
188****24fb771b7
With the help of keyhunt I was able to determine the private key in a minute. And a few days before the new year I successfully got access to the coins))))))

On the second wallet 1PkM3Hgw7xDrBeGWhs2zdNXSmam2BikAKX the situation is more complicated, but I had outgoing transactions from this address. I decided to use the algorithm "Baby Step Giant Step (BSGS)"
Knowing the first 31 characters of the key, I calculated the WIF ranges and HEX ranges.
5K***wh111111111111112n4ctq
5K***wi111111111111113ZdYQK
b67****fe3eb1fcb518100e5daa7cc30
b67****fe40ede330771f36e75571c83
Total 43211566443142029589303379 HEX key variants.
Unfortunately, I was not able to quickly restore the key. I have a very powerful computer, but with my speed of 506 Pkeys/s (506359533900084483 keys/s) the required time for selection is more than 2 years.

I have studied all the best programs for brute-forcing a private key, and BSGS is the fastest algorithm at the moment. I do not want to look for the key for 2 years. I decided to postpone the search for the key until programs with greater performance than now appear. Perhaps quantum computers will be able to do this in a few seconds in a couple of years.
By that time, Bitcoin will be worth much more. So I will only benefit from waiting.
I hope my experience in recovering keys will help someone recover damaged keys.
Happy New Year and Merry Christmas to all!!!!