I am puzzled by this as well. Their are roughly 2.7 MM shares outstanding, of which over 1.4 MM are controlled by the estate. I do not see how any estate shares could have been sold. If the estate does move to sell they will either act to sell the whole company or sell in a single transaction with the company mgt. (That happened with BBSI) So are there are only 1.3 MM shares available to trade at present, so there must have been buying and reselling which implies more than one large buyer. Perhaps there were some computer programs involved picking up on the large percentage price change. My initial thinking that there was one large buyer coming in to a very thin market accumulating. I have seen this many, many times in thinly traded issues. But this must be more complex.
As pointed out it is likely there are some new large owners.
I think we witnessed a stock newsletter pump and dump. It seems there was some hype about 3d printing and a flurry of posts on twitter. In spite of the momentary hype, there is real value here, in my opinion.
Looks like most of it happened right at the opening bell and the few hours succeeding it. Major block trades, and then a slow dumping. My guess is that some people wanted in bad, and then existing shareholders, seeing the sudden upside, slowly started unloading their positions. I bet there is a new set of major owners of the float now. This has gotta be a good thing.
After holding for a few years and seeing the past hx of this price action in NSYS I choose to sell 2/3 of my position on the spike. Now that the frenzy is over, maybe now is the time for more orderly accumulation.