Just got a call from my broker (TD). They have been looking into the strange 500-share trading acitivity in TDC. It has taken a few days because my broker contact was stumped - he took it to TD's trade specialists and they also don't understand it. They have never seen an order execution type or trade strategy with this behaviour, and they describe it as a "mystery."

Their best guess - similar to mine - is that a large shareholder is exiting in such a way as not to disrupt the TDC market.

But they said this particular approach would be VERY expensive, as the exchange charges fees for EVERY trade.