What is a white round pill with a M that has a square around it on one side and a 15 on the other side?

Not medical advice: A white round pill with imprint squared M and a 15 above a score on the other side is 15mg oxycodone, a narcotic painkiller.

Wednesday, February 01 2012
Source: http://www.drugs.com/imprints/m-15-5065.html