I could be wrong, but maybe this is from Blockchain.info old wallets. See if your string looks similar to this?:

https://bitcoin.stackexchange.com/questions/119979/decoding-a-base64-wallet-from-2014

Also, regarding your 32-character string. Could you show us a few characters from it? It could possibly be either a Bitcoin address or a blockchain.info wallet ID (which I believe should have 36 characters if you include the 4 dashes).