Anyone have any info on this Toronto Token?

So my grandfather just gave me four of these older tokens, and I have no information on them.  I haven't seen anything on ebay, and google has showed me three different tokens like it but not this exact one.

They're extremely light so I figure aluminium or at the very least some sort of tin-plated plastic, and they're just under 4cm in diameter.  

Any help would be great.

thanks

My guess would be that this token was issued when the new city Hall was opened. Google for Nathan Phillips Square...