It looks like you're referring to a specific version of (v1.5.8), likely a build from the GOG platform.

"Mount & Blade II: Bannerlord v1.5.8 was a major update in the game's journey toward its 2022 full release. This version focused heavily on stabilizing the sandbox experience, introducing the which allowed players to start their journey without the constraints of the main storyline. It also brought significant improvements to the battle terrain system , ensuring that the maps players fought on more accurately reflected their position on the world map, and added several new armor sets and weapon balances to the Calradian frontier." 2. Technical / Patch Note Highlights

Since you mentioned a specific file string format, if you are looking for help with a technical issue or installation for this specific version, please let me know!