The back half is the actual transformer tank. With the cover open, the primary connects to two large posts on the left side and the secondaries leading to your house goes to three smaller studs on the right.
Ahh I see. Interesting to know how it wires up! At my school there's a 1950s incarnation of a padmount transformer. It's three regular hot water tank style brown transformers in a concrete hut about 15-20ft tall with an open front that's secured by a chain-link gate. You can hear the transformers buzz when you walk by.