This is a handle for a safety razor head with an M5 thread.
It's designed for a threaded insert; hole size for it is ø6.4mm x 10.5mm.
I uploaded a version of the model that includes a structure supporting the handle from the side via very thin bridges that can be easily cut off afterwards. This is to prevent the thin part from falling over or shaking too much during printing.
The author marked this model as their own original creation.