Round Pill Costume I Found A Little White Round Pill With ST Imprinted On It, Can Someone Tell Me What It Is?

I found a little white round pill with ST imprinted on it, Can someone tell me what it is? - round pill costume

I have tried to find the answer in different sites pill identification, but I get no clear answers. So, if you know the answer, please let me know as soon as possible. Or if you know a great website that shows pictures of the pill may also help. Thank you in advance.