The 1-4x likely denotes a version range or a multiplier for assets (e.g., 1.4x scale or resolution).
The .7z extension is a high-compression archive format created by 7-Zip . bdys-1-4x.7z
In UAI/NASTRAN , BDYS (and BDYS1) refers to Bulk Data entries used for defining boundaries in finite element modeling. The 1-4x likely denotes a version range or