Designed to cover the wiring connections on a Mean Well LRS-350-24 power supply and provide a mounting location for an IEC320 inlet socket.
Specifically designed for this power connector: https://www.amazon.com/gp/product/B0895T9NXF/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Requires 2xM4x8 screws to fix the box to the PSU.
The author hasn't provided the model origin yet.