Bo2offlinespmpzmclientv37z →

: Files with such long, specific alphanumeric strings are frequently found on peer-to-peer (P2P) or file-sharing sites. Always ensure you are using a reputable community source, such as the Plutonium Project , which is the most well-known and widely vetted "client" for older Call of Duty titles. Call of Duty®: Black Ops II on Steam

The v37z suffix likely references:

This is why the modding scene exists.