Oval green scored tablet imprinted SL on one side and 604 on the other side is SUSTAINED-RELEASE
GUAIFENESIN 600 MG and
PSEUDOEPHEDRINE HYDROCHLORIDE 120 MG. According to one database, this imprint was discontinued in 2001.
More info:
http://guaifenesin.and.pseudoephedrine.drugs.com/
I'm not a pharmacist or a medical doctor. This message is not medical advice nor is it an offer to provide medical advice. All drug identifications should be validated by a licensed MD or pharmacist.