The 18650 battery case/holder. Battery contacts are made from the nickel strap 8x40mm. The stamper is used to form the good battery contacts. I recommend to pre-solder straps with the usage of Ni soldering liquid for the easy wiring. Lets do it before inserting them to rectangular holes on both ends of the case.
Nothing special. Print it from PET-G for the durability and some flex. The stamper with 80% infill to make it strong.
The author hasn't provided the model origin yet.