This small embossed HYNSON, WESTCOTT and DUNNING bottle once held mercurochrome, an antiseptic commonly used in the 20th century. The bottle would have a glass stopper/applier, which is not with this bottle.
I did not find when the company was formed. They did produce a product, perhaps the same or different product, that was sold in a cobalt blue glass bottle. I've not found one of those.
Here is a vintage or antique ad for mercurochrome.