Hey Pick,
Nice find! I have found some that are kinda like that. I think they were just unembossed meds. maybe pills, put in rounded bottles so that they would'nt get hung up. Somewhere upstream from where you found that there is most likely a dump that it washed out of. It is old enough that if you find the dump you might find some real goodies. Good luck on the artifact and bottle hunting!!
Twig.