This is one I'm really curious about!

Sometime last year my Dad & I were probing around looking for CD 143s on the local CP line, when I hit something with my pitchfork. I continued to probe around it to get a grasp for where I should dig in order to get it out, and soon discovered that it was huge - probably somewhere around 8' long.

So, we spent several minutes trying to get whatever it was out of the ground, and soon discovered we had stumbled across one of those "W" signs we often saw along rail lines. I sincerely had no idea what these signs meant, but this one seemed to be more than just a tad older than the ones still in service, and I liked it! However, it was 8' long, at least, and therefore wouldn't fit in my dad's car. So, we hid it, intending to come back in a few days and retrieve it.

Fast forward a year. I had completely forgotten about the piece, until we stepped into a railroad museum just to look around for a few minutes, and I saw a sign showing the different railroad signals, and what they all meant. The "Whistle Post" was one of them - apparently indicating to the engineer of the train that he'she should sound the train's whistle, as an intersection, or otherwise hazardous area approaches. This jump-started my memory, and I decided that I had best go back ASAP and pick up that sign before it rusted away into oblivion.

So, we did just that. And here it is. The thing is solid iron, and the "W" is punched out of a metal plate instead of being painted on like the newer ones are. I've never seen one in service. My question is, does anyone have any idea how old this is? I assume it's a strictly Canadian whistle post design, as I've looked elsewhere on the internet, and none of them hae the octogonal sign shape like this one does. I believe this is a Canadian Pacific design. Any help would be appreciated!