Quote from: racquemis on December 05, 2017, 10:43:37 PM

Quote from: Macrum_reborn on December 05, 2017, 08:02:39 PM

Since the backup is on an external drive, I guess that I maybe once removed the drive to soon (without safe removal). About the version, I am not sure, but a rather old one, as this happened back in 2014 / 2015. Until recently I did not check my backup...

This makes me think your harddrive is "cluster f*cked".

A file can be corrupt in two ways:

1 - The software (in your case bitcoin core) had a failure when writing the file
2 - Your harddrive failed and corrupted the file

In case 1 you can ask for extern help -> copy the file, hand it over and let somebody try to recover it
In case 2 you can NOT ask for extern help by handing out a copy of the file since you can not hand over the harddrive index and cluster build.

In case 2 (i am 90% sure this is your case) the only thing you can do is hand over the complete harddrive to a specialist who will try to rebuild or restore your harddrive index and clusters with special software.

If i where you i would look for a local company that can rebuild broken harddrives and ask them if they can recover the file, most of those companies do a quick scan and tell if it's possible or not within 1 hour.

OP can at least check if his wallet.dat encryption key is intact.
Following the steps here: https://walletrecoveryservices.com/limited/
If his encrypted_key is larger or less than 48 bytes, well god-bye Mr. wallet.dat.
Maybe Dave has some special methods to recover it though.