In technical and medical literature, "3.5.1" frequently appears as a section header for specific data reports:
There are various "Heist" related editors used for game level design or character customization (e.g., for games like Payday or GTA ). If this is a modding tool, version "3.5.1.z" would be a very specific development branch. Heist Editor 3.5.1.z...
The AMS/EPA Regulatory Model (AERMOD) uses specific versioning for its technical guides and formulation documents. In technical and medical literature, "3