Figuring out the core wallet version when backing up an old wallet

How can you find out what version of the core wallet was used when backing up an old wallet.dat file?

You've posted a few topics regarding old wallet.dat files, have you received it from somewhere? Because it's best to be transparent on that matter so you'll not end up asking questions that are just causing "X/Y problems". Anyways, you'll have to get an untouched copy of the wallet.dat file which wasn't loaded to any updated client yet. So keep a backup of the original file and only use/load a copy of it to keep it fresh. Then to check: Restore a copy of that wallet.dat file, wait for it to load and open your "debug.log" file. Find the line indicating that specific loading wallet process and you should find the "last client version" near those lines. Note: it should start the wallet name that you've set. e.g. (fake wallet created with v0.20.1 loaded to v29.0):