Not entirely sure what to make of it but it is interesting. The 3 coins do seem to have some correlation, especially a simultaneous surge in Sept-Oct followed by a quick decline. the 1979 IYC silver proof seems to be underperforming for quite awhile now, looking at the bottom of the chart going back to 2012. I find that interesting considering that it's a fairly rare coin with a wide range of potential collectors due to those collecting the IYC series of coins from around the world (The China IYC is one of the rarest). My personal guess would be that its underperformance is due in part to it being an "older" MCC (1979) that had already run through a cycle of demand and is now on the backburner as not a lot of new collectors are taking up the IYC series which ran from 1979-1982. (Whereas for comparison-- the Panda series is still being released each year, so new collectors are joining all the time, adding more demand for the older ones)
