cobalt blue milk of magnesia looking bottle

After 2hrs I cannot find anything about this bottle, its ur standard 7in darkish cobalt blue milk of magnesia looking bottle But is had no "philips" markings or anything except at a raised 16 on bottom underneath, not in middle but towards the edge. Or could be a 91 depending on which way u look/hold it. Its driving me nuts..found in a old bottle or just plain dump site 15+yrs ago in CT... k3yrltr@aol.com thanks