I spoke with a very accommodating gentleman at Kitco regarding the chart you posted.
He was familiar with the phenomenon and had seen it before. I was impressed that I reached him so easily and that he discussed it so openly. From past discussions at Conventions with Kitco spokesperson Jon Nader I have never trusted that Kitco was on the side of gold.
He explained it is very difficult to go back and try to find out who/what made the trade. most likely it was a Market Maker doing the trade. these MMs could be big Hedge Funds, Banks, wealthy individuals, algorithms…. For a fee these MMs have access to see the Order Books showing stops etc. quite often the tactic is used by someone that wants to manipulate the market either up or down for the purpose of accumulating… or disgorging.
None of this was really news to me and I would accept that what he described is often the case.
Left unsaid, and probably unknown, is whether the tactic is used to signal others to assist in the trader’s purpose.