For those interested, I just want to post an update: Since 2020 I was able to confirm, that the test set I initially got is intended for thesting the BAe Hawk's attitude and headinr reference system (AHRS), namely the AHRS-6000:
I was even able to obtain the matching displayemen gyrsocope (plenty are available for a low price). These are really masterpieces of mechanical engineering with two independent gyros on a platform - one used for pitch/roll leveling and the other one for heading. Much harder to get hands on was the control box called "Electronic Control Amplifier", but finally I got one (shown with the test set's cables attached already):
And after some investigation and creating cables I was finally able firing up the system and thanks to the test-set I am having quite full control on the servo loops, handling of earth rate and I can peek into the system while running:
Also visible in this picture is the attitude indicator which is driven by the system and which was discussed in some posts before. So if there are questions, just reach out and a second of the ECA boxes as a backup would be highly welcome...