Phenian,

Chollima 091

Nr. б/н

This is a unique vehicle. It looks different because it was built with the frame of Chollima-316 and hence has larger windows and lower floor level. It also has a destination blind instead of stickers to show route like early Chollima-316.
It is the last 'Chollima-091' built, unless if it has a different designation.
The (21) is the factory number.
Satellite images (6/6/2021) show the trolleybus factory has laid down 10 very long articulated frames at 21-22 metres and 27 frames for 12 metre trolleybuses.

Source: https://i.imgur.com/Q4IaY8R.jpeg