The give-away is that there are windows. Chimneys do not need windows!
The structure is actually a shot tower, was built in 1882, and is one of only two remaining in the state. The other is the one inside Melbourne Central. This one is reputed to have been the tallest in Australia, and is also notable for the polychrome pattern brickwork (look up)!.
Shot was made by melting lead and then pouring it from inside the top of the tower so that it fell in small streams, which naturally became droplets. The droplets were shaped and solidified as they fell from the top of the tower, and were cooled by dropping into water at the bottom. The shot was then dried, sorted, polished and bagged.
The tower was a landmark of the area and was apparently used as a visual marker by pilots flying into Essendon Airport.
The cache is fairly small, so not really room for swaps, but bigger than a micro.
Despite the structure reception should not be a problem.