The best powder I ever shot, was from a 5 pound can I acquired back in 1975 from Cliff Hunter in Vancouver, BC. American Dead Shot was the brand. I read somewhere, that factory blew up in 1895 or 1898 and was never rebuilt, thus at that time, the powder was possibly, 80 to 100 years old.
The powder was FF grade and gave me the BEST accuracy in my slug shooting .50 Bauska Barrel, compared to all the other powders we had then, including ICI, C&F and GO. There was no buildup of fouling in the bore and the shooting was quite clean, even though the Lyman bullet I shot had small, "modern" grease grooves. They were shot without wiping.
Dead Shot was supposed to be only in 2nd place compared to C&H's Diamond #6 as a sporting powder in the late 1800's. Sure worked for me.
The powder granuals were hard, clean, angular and sharp sometimes on one end. There was absolutely NO dust in it at all. Holding a palm full then pouring it from your hand back into the barrel, left my hand perfectly clean - absolutely no dust whatsoever. Of course, I shot it all up and threw the can away. It lasted only a few weeks, maybe a month. I shot a lot then.