Sometimes going through cups give you interesting facts that is not apparent. Unfortunately, unless one digs into the archives, sometimes very little can come in the way of confirmation of these information, so the results remain piecemeal. The existence of some of these items, however, do tell us that something happened or some unit existed - even when we thought it might not be the case!
An example of this is this cup
It very specifically tells us is for a military exercise in training transport units to ford rivers. It's unfortunate that there is no date on this, but one would assume that this is an earlier rather than later cup given the style and shape. Who knew the military conducted such specific exercises? It makes sense, but it's not something you find recorded in official histories and that sort of thing.
Or take the example of the idea that the Japanese generally ignored snipers. The IJA didn't develop a specific sniper rifle until the late 30s. However, here's this cup:
This is in the style of earlier cups - Russo Japanese war or WW1. Sniper activity is certainly common by then - you had trench warfare accounts in Europe that is full of stories of snipers doing their job day in, day out. The concept of sniper must exist in the IJA too, even if they didn't have a specific sniper rifle. Perhaps this is for a soldier given the role of a sniper, however unofficial, and he came back victorious? Given the style of the cup it's really pretty unlikely it's a late 30s cup, in time for when sniper is supposed to have been more institutionalized in the IJA. So this must, I think, suggest a rethink on longer term development of the sniper role in the IJA.
They also give us information on how these cups sometimes came about. For example, this cup (and another that sold a few weeks ago):
The label under the lid clearly spelled out why the cup was made - basically, if you hand out cash that was given by the emperor to the troops, the money is going to be gone once the soldiers spend it and there will be nothing left. Instead, regimental commanders decided that they'll spend the money on making cups for everyone to take home. I'm not sure how the normal soldier on a regular salary would react to this, but perhaps some would've liked to see the extra cash! But of course, they did achieve what they wanted - by making the cups, we now possess physical goods that confirm the events and commemorate their acts. Good job too in deciding to use pewter, which would damage nearly as easily as some porcelain cup. That, I guess, is mission accomplished by those commanders who made that decision.