Usage
forensics.exe file1.rbxl ./dir/file2.rbxl ...
Expect output like:
file1.rbxl,664,670
./dir/file2.rbxl,536,539
Supports rbxl or rbxm files saved with Studio versions 47 thru 
~666 .
How did I do it?
When you save an rbxl file on Rōblox Studio, many properties will be saved with each in-game instance. Even ones that you don’t usually modify. For example, Workspace saves with:
-
AirDensity, -
AllowThirdPartySales, -
DecreaseMinimumPartDensityMode, -
StreamingIntegrityMode, -
TouchesUseCollisionGroups, -
TerrainWeldsFixed,
… and so many more.
New properties get added to Workspace and other classes every version.
Even if you modify an older rbxl file, the new properties will also be added.
My program collects the class names and their respective properties and uses them to estimate a range of Studio versions.