Things You'll Need
Instructions
Examine the bottom of the bottle. The pontil scar is the half bubble that goes up into the bottle. If it's an open pontil scar, which means that it came from the punte tube, it is a mark of bottles that are 1600 and older, up to the 1880s. This pontil scar is caused by taking the punte iron (though which the glass is blown and held) and breaking it off the bottom of the bottle. This leaves the telltale impression, which will be rough and potentially discolored on older bottles.
Examine the bottle neck. Before the 1880s, bottle necks were made by taking hot glass and putting it against the bottle where the glass was hand-worked with tools. This means that the lips will be crude and uneven, with the bottle necks often being uneven and definitely hand-worked.
Look at the density of the bottles. By the standards of today the bottles will be very thick, since the glass was meant to withstand multiple fillings and a lot of use over time, since glass was much harder to make in the past before machinery and automated processes.
Compare images of the bottle to other images of similarly aged bottles. Any identifying marks in the glass, the color, bottle style and other details will mash up with other bottles of the same time frame in Africa.