You may want to have a look at which characters you find in your encoded string. As of https://en.wikipedia.org/wiki/Base64 Base64 uses all A-Z, a-z, 0-9 and two other characters, usually + and / and = for padding.

Base58check uses only a smaller subset and avoids symbols that could be ambigous in most type faces. Additionally it has a partial hash checksum embedded. See here for symbols of Base58: https://learnmeabitcoin.com/technical/keys/base58/

In some cases it might not be possible to distinguish Base64 from Base58 depending on the sample string size. Base58check should be distinguishable because it must pass the checksum test as long as it's not crippled.

A WIF private key is composed of a prefix byte, the private key bytes, optional compression indicator byte and finally a partial hash checksum of four bytes, then all encoded with Base58. See e.g. here for details: https://learnmeabitcoin.com/technical/keys/private-key/wif/

I haven't used Bitcoin-GUI as now Bitcoin Core was called in those early days of 2010. I used Bitcoin-GUI on Windows OS in 2011 earliest. In 2011 I didn't fiddle much around with it, just mined some coins and moved them around. I didn't touch private keys at that time at all, didn't see a need for it until I had to recover a wallet from a dying harddisk many years later.

I don't think the standard Bitcoin client software ever asked for a wallet encryption passphrase when it was opened. But I may not understood what you were writing about your early wallet.

You may want to have a look at which characters you find in your encoded string. As of https://en.wikipedia.org/wiki/Base64 Base64 uses all A-Z, a-z, 0-9 and two other characters, usually + and / and = for padding.

Base58check uses only a smaller subset and avoids symbols that could be ambigous in most type faces. Additionally it has a partial hash checksum embedded. See here for symbols of Base58: https://learnmeabitcoin.com/technical/keys/base58/

In some cases it might not be possible to distinguish Base64 from Base58 depending on the sample string size. Base58check should be distinguishable because it must pass the checksum test as long as it's not crippled.

A WIF private key is composed of a prefix byte, the private key bytes, optional compression indicator byte and finally a partial hash checksum of four bytes, then all encoded with Base58. See e.g. here for details: https://learnmeabitcoin.com/technical/keys/private-key/wif/

I haven't used Bitcoin-GUI as now Bitcoin Core was called in those early days of 2010. I used Bitcoin-GUI on Windows OS in 2011 earliest. In 2011 I didn't fiddle much around with it, just mined some coins and moved them around. I don't think the standard Bitcoin client software ever asked for a wallet encryption passphrase when it was opened. But I may not understood what you were writing about your early wallet.

You may want to have a look at which characters you find in your encoded string. As of https://en.wikipedia.org/wiki/Base64 Base64 uses all A-Z, a-z, 0-9 and two other characters, usually + and / and = for padding.

Base58check uses only a smaller subset and avoids symbols that could be ambigous in most type faces. Additionally it has a partial hash checksum embedded.

In some cases it might not be possible to distinguish Base64 from Base58 depending on the sample string size. Base58check should be distinguishable because it must pass the checksum test as long as it's not crippled.

A WIF private key is composed of a prefix byte, the private key bytes, optional compression indicator byte and finally a partial hash checksum of four bytes, then all encoded with Base58. See e.g. here for details: https://learnmeabitcoin.com/technical/keys/private-key/wif/

I haven't used Bitcoin-GUI as now Bitcoin Core was called in those early days of 2010. I used Bitcoin-GUI on Windows OS in 2011 earliest. In 2011 I didn't fiddle much around with it, just mined some coins and moved them around. I don't think the standard Bitcoin client software ever asked for a wallet encryption passphrase when it was opened. But I may not understood what you were writing about your early wallet.