This is a mount for a Supernova E3 Tail Light 2 (N-TK2-BLK) with 2-bolt attachment.
The bracket fits the saddle of the 2016 Hardnine or Hardseven bike models from Haibike. Probably also for other models. The holder uses two existing screw holes to fix it to the saddle, whereby the original screws have to be replaced by suitable longer screws, e.g. SPAX.
The assembly of the taillight itself is done by original M4 screws directly into the borings of the bracket.
For the cooling of the LED I've constructed appropriate ventilation tubes.