I was associated with a trolley museum in Illinois, and we operated an open streetcar from Rio de Janeiro. It had a fare register similar to this one, but it was marked in Portuguese. The register illustrated here had a widow showing "IN"; the other probably showed "OUT". Our register had "IDA" and "VOLTA" for coming and going, the two directions of a trip, so the fares would be registered in each direction separately. No one in our group spoke Portuguese, so we didn't know which was which. In our chat to riders, we would say it did not matter, because we didn't know whether we were coming or going ...

PS: The "IN" and "OUT" were selected by the twist thumb piece at the lower left of the register.

That circular gadget above the doorway is a fare register. When a passenger boarded and found a seat or a place to stand, the conductor would approach them and collect the fare, reach overhead to pull a cord which increased the count displayed, and pocket the coin.

At the end of the day he turned in the coinage for the amount shown on the register.

Needless to say, there were unscrupulous conductors who under-rang the register, which led to the invention of the farebox into which passengers directly dropped their fares to be counted.