It could represent a version like v1.7.3 with a "2x" modifier (possibly referring to a 2x speed mod, 2x texture pack, or a secondary revision).
In some technical contexts, these numbers represent build dates or specific hardware revisions (e.g., March 17th). 17-3-2x.rar
The "2x" suffix is frequently used in community-made patches for games to denote "Double Resolution" or "Double Rate" (e.g., Nexus Mods often hosts such files). Safety and Handling It could represent a version like v1
If you have encountered this file on a forum or file-sharing site: 2x texture pack