After accessing a wallet on Blockstream Jade, you will be shown your wallet's fingerprint above the menu bar. This alphanumeric string corresponds to a specific wallet, and is useful for recognizing which keys you currently have loaded onto your Jade.
Passphrase or SeedQR users who may access many different wallets should take note of their wallet(s) 8 character fingerprint and check that the fingerprint matches after logging in with a specific passphrase for example, to ensure they are interacting with their intended bitcoin keys. A recovery phrase with two unique passphrases added to it will lead to different wallet fingerprints, so this is useful for checking if you have a typo in your passphrase entry as well.