The contains is like this. U6FsdGVkX12bI6G2vb99R08I3RuPa465RPmUr3sngK08iY3bBqVEZb7YBHHPzcnXG8JcgplbopG
05IrXb1yht76vHuXEvIjtbwe8yVdvHb3n+dgQiu5THacmB14aOLP4nmtb7aezoHh92QQosvv4X4qM
Before going further, since you don't know where it's from, do you still know the password of that wallet or at least some parts of it?05IrXb1yht76vHuXEvIjtbwe8yVdvHb3n+dgQiu5THacmB14aOLP4nmtb7aezoHh92QQosvv4X4qM
Because the contents look like in encrypted form and as you know, only you (the owner) can decrypt it since even the wallet developers don't have access to it.
(don't PM or post the password if you know it)
Edit: The end of the line has no " -- " on it.
Do you mean " == "?Because not all base64 strings end with it.
Please tell us the wallets that you already tried, encountered errors and other recovery methods that you've used to recover the file, etc.
Because this may be an "XY problem" if you tested that already to the suggested wallet.
Yes, The schildbach wallet contains " == " at the end of it instead it has FILEEOF
The backup is structured like schildbach wallet but different ending at the end of the file.
