Help me understand this antique

I just came across an old wooden box. I think it is a great find, but help me undersatnd some of the writing on it. The box has finger jointed corners and cast metal handles on the ends.
It is about 18 x 24 inches and 10 inches deep.

The writing reads as follows (with my asumptions in brackets)

To Canadian National Rwy (that part is obvious)
c/o Signal Stkpe (I assume that means Signal station keeper)
Pt. St Charles Montreal
Canada
on.T.2A/sio 5/878 (or it could be 5 1878 but CN was not around back then)

(what is a signal station keeper? the same as a station keeper?)

I will also add it smells like an old wooden caboose interior, of which I have been in a few

Any help would really be appreciated.

A SS or signal station was a switch or interlocking tower.

The SS controled the switches, interlockings, signals, - and on the NH electric line circuit breakers - in the block.