An outstanding acquisition, sir!
The product was extremely well named, as it was truly "unique," especially for the era - - something over 100 years ago, IIRC. It does extremely well in a VERY wide variety of handgun cartridges, and will also serve in shotshells and gallery rifle loads.
I have my favorite loads of Unique in .45 ACP, .45 Auto Rim, .455 Webley, .45 Colt, .44 spl, .41 mag, .40 S&W, .357 mag, .Super .38, .38 spl, .38 S&W, 9x19mm, and .380 ACP. I use some other powders as well, but I COULD get along with only this one pistol powder.
Some dislike Unique, citing it as a "dirty" powder. Well, it DOES leave a bore looking a touch dark after a few boxes, especially with lead bullets. But, really, this is mostly soot, and not true fouling. A single pass with a Bore Snake or a dry patch on a cleaning rod gives a pretty clean barrel. That and a bit of toothbrushing on breech face and feed ramp keeps you i9n business for literally hundreds of shots.
Use your treasure in good health and safety.