Apothecary bottles are fairly common - consider the number of pharmacies that had dozens, if not many more, on their shelves. Clear glass is the most common - examples in other colors are more desirable.
The condition of the labels is also important.
The presence or absence of a pontil mark on the base probably adds a bit to value.
The most desirable are those that have labels for controlled substances (heroin, morphine, etc)
