This blue, oval pill imprinted with M 312 is a Verapamil hydrochloride 180 MG Extended Release Tablet, per the NIH.
Verapamil Hydrochloride is a human prescription drug. The active pharmaceutical ingredient is verapamil hydrochloride and is classified as, "Calcium Channel Antagonists [MoA], Calcium Channel Blocker [EPC]."
This pill is made by a total of 4 firms: (1) Mylan Pharmaceuticals Inc., (2) Physicians Total Care, Inc., (3) Mylan Institutional Inc., and (4) REMEDYREPACK INC.
There are 5 other blue pills that with a similar imprint: "M 312". They may be a different dosage of the same drug or a different drug entirely.