My information about small D came from Shanghai. A US customer asked me to get him a sheet of small D coins from Shanghai after they started showing up in the NGC pop reports, when I asked around I learned there was a controversy about its authenticity, which was also discussed on this forum. I told the customer what I learned and he still requested I get him a sheet since NGC was grading them he was fine with the risk, he graded the coins and kept 4 for his collection at zero cost basis. I emailed him about this thread and he said he only has 1 left and will ride out whatever happens. I have never owned one for my collection or sold a slabbed coin, because controversy existed about the coin, I don't want to sell a coin to a collector that may turn out to be disaster unless the customer asked me to source the coin for them.
There are a few coins that have controversy, some people like to get involved with those coins, while I tend to avoid those high risk/high rewards scenarios. There is a 1978 CU/NI macau grand prix coin that I started accumulating in 2009-2011, kruse book stated a mintage of 11, but I somehow accumulated 6 pieces at an average price of $700 over 3 year period without much effort. I and those that sold the coin to me knew the mintage number had to be wrong. I sold several on ebay but stated in the description that stated mintage is probably wrong so don't blindly buy because you are expecting a 11 mintage coin for only $2000. Another one that has a lot controversy is 1984 silver pagoda set mintage of 260, some believe the mintage is closer to a 1000. Another example is the 1996 1oz gold russian tiger with stated mintage of 1000, but that coins is so common that everyone is sure the mintage is a lot higher.
Those that want hard facts will be disappointed with modern chinese coin market, because I don't believe we will ever get those beside small updates to what has been already published, all we can do is study availability, pop reports, prices, dealer patterns, etc to determine what is truly rare and authentic. I worked as an engineer back in 2001 at a factory that produced $30M of revenue per day, ask me what I remember from that year, I can't think of single hard fact that I remember about production numbers, yields, cost metrics, average selling price, unsold product, etc. despite being an analytical person who had access to every database about our production metrics. If I can't remember and given the china mint folks probably had access or tracking to just a fraction of the information and less education, I have to assume the facts will never be discovered.
I don't rely on anyone opinions on what is the rarity of a given coin, I do my own research and block out all the noise of collectors, investors, authors, dealers and promoters. What I do rely on is others opinion on whether a coin variety is authentic especially if it is trading at significant premium or if the mint packaging is different from what I have seen in the past.
I will watch this play out from the sidelines with nothing at stake.