If I were still a reloader like I was 25 years ago, I would make some .38 special loads with that stuff and fire them through a 357 magnum revolver.
Starting very weak, as if it were Bullseye, and working my way up.
I was looking at few of my older containers of Unique powder (Hercules Era cardboard tubes). All of them had lot numbers like that for Unique. Example being UN 411 (1994 dated). Conversely I have an old Hercules Green Dot 4lb cardboard container that has a lot number of GD 206 stamped on the side much like yours. If I was going to use it I would treat it like Unique start low and work up.