Hello Elias,
as for now there is now way to verify the firmware of a NK Pro. As @solucion said, it is possible for NK Storage though. If you are not trusting the firmware of your key, you may can flash it yourself in future. On the github page we publish the firmware. I did not tried the short instruction on how to flash, so for now I can not say, if it works properly.
I try to came back here as soon as I tested the process!
Kind regards
Alex