Bryston BR-20 screws

 I purchased a used BR20 preamp through TMR audio and was hoping someone could help me.

Everything seems to be working fine, accept the remote control will not communicate with the BR-20. I've been in contact with TMR and they contacted Bryston who I believe is sending out a new remote for me to try. I still think there's possibly an issue inside the unit, since when I move the unit around I hear a loose part in there. I was asked by TMR to unscrew the cover and see what I could find, but I'm not sure what type/size screw head it is. It looks like a allen key or a tork head, but they are very tiny, and I don't want to use the wrong size and strip the screw out. Any help would be appreciated !