Whites Liniment

So I went to an estate sale and found this old bottle (with a glass stopper) of Whites Liniment. The label reads Alcohol 10%, Opium 1 18/100Gr per Fluid Oz.. The box reads 2 FL. OZ. and a price of 50 cts.
Here's the thing, it's full. You can tell it was new because it came in the box. The lid is very tight and I am afraid to force it for fear of breaking it. I am wondering two things, because it 's full is it allowed to be sold and where can I have it tested to see if it is the real thing, which I think it is.