Great idea - is that really an old medicine bottle? It certainly is old! The light is very harsh, and the reflections & strong shadows steal the spotlight from the subjects (no pun intended!) I've found that reflecting the light off a piece of white foamboard helps, or putting paper or fabric in front of it softens and reduces glare. Thanks for being creative on your subject choice!
I like your idea. The shadows are real killers here, as are the reflections. . If you can't light the background, then you should move the subjects farther away from the background to minimize the shadows. I think the plastic cup detracts from the image - I get it without the cup.
The title is interesting and it took me a while but I had figured it out. The old bottle is veryunique and had it been presented a bit more creatively, It could have acted moreso as a central focus. Since the title refers to the closure, there is no need for the plastic cup in the forefront which really glares and does nothing for the shot. It looks like you got some flash on all of the subjects and could have eliminated that with the use of a desk light with a sheet over it. The subjects are too centered and the background does nothing to add to the photo. On the other hand, the focus is not too bad.