Maybe this will help:
On the back there are four screw-type brass connectors. These four are labeled
B3, L1, L2. The fourth one has no label but has a screw in it screwed to a metal piece.
There are three tab-type (push-on) connectors labeled BU and a 5 next to it
BR and a 7 next to it, the third one has no label, but an 8 next to it.
Does this help?