I recently had a prescription filled for 7.5 vicoprophen. I don't like carrying the whole bottle when I leave the house, so I usually make sure I grab a few for my purse. Yesterday I noticed a different pill among the group. It is the same size and shape as the vicoprophen but this is light yellow and blank on one side. The other side has a verticle line with M on the left side, and 3 on the right. I have not been able to find out what this pill is nor where it may have come from. Can someone please offer any suggestions? Is it maybe some type of vitamin? Thank you!