Yes it is a postcard. The Erie "mainline" ended in Jersey at the Hudson River, but they did have docks for launching carfloats. Erie had 2 yards East of Jersey that were isolated and only reachable by carfloat. They were 149th St. in the Bronx and 28th St. in Manhattan. There were other locations where the carfloat would dock at a pier and unload. The cars would remain on the float though, no trackage. The back of the card says Erie has 240 boats in it's "Navy". Seems high to me, but that what it says.
I knew they had some tugs. But 240 sounds high. Maybe that included all their barges, etc? Boxcab E50