[zztadams]

I have some flour stored in an unnamed container. Is there some way to tell if it if SR Flour or Plain Flour apart from cooking with it?

[curlybenswife]

Only thing I can suggest is cooking a small amount or looking at the grains ones courser than the other but if the tubs aren't even colour coded you don't have a lot of choice to do anything other than cook with it I'm afraid.

[maggiemae]

I have some flour stored in an unnamed container. Is there some way to tell if it if SR Flour or Plain Flour apart from cooking with it?

There are two ways to tell! One is to rub a bit between your fingers; the self-rising flour will feel a little gritty. The other way to tell is to taste it - the self-rising flour will be salty.
Hope this helps!