Well, I put it in the device and it performs just the same as stock battery - which I am not sure is genuine, though, - 5 hrs of video playback (not non-stop, spent some time switching between series and checking battery-eye) on minimal brightness.

Also - got a very nice offer on used Asha 200 in my town, is it a good idea to use it as a charger for bl-5js? It will cost me ~10$.