This is a new case for a Raspberry Pi 3B with the new form factor LiFePO4wered UPS. (https://lifepo4wered.com) To be clear, this UPS is not on the market yet but will be available soon. Edit - Just added a slight variation on the bottom of the case. The "Even Standoffs" version has all the standoffs the same height so you can just use the standoff as the nut for the M2.5 screws that hold the UPS board. I moved the uneven standoff version to the last of the images and the file itself should be clear from the naming.
The fan cutout is for a top mount 30mm fan. I use a Pi-Fan I got from Amazon. It doesn't put out a lot of air but anything helps and keeps the air from going too stagnant in the box. The baffle/skirt is there to help direct the air towards the CPU and IO chips. M2.5 screws hold down the Pi and M3x25 screws bolt the case halves together. The UPS has bolts and nuts to attach it to the Pi. Edit - the old version of the bottom file has the uneven standoffs - That's why the standoffs are shorter for the two mounts opposite the HDMI side of the Pi board - to allow room for those bolts and nuts. They still have a printed M2.5 thread in them though. The "Even Standoffs" version has them all the same height.