Wehrmacht soliders used lots of different types of ink bottles. Excavated finds from dumps in former Wehrmacht positions in eastern Europe have turned up a wide variety, not only German ink but products of other countries as well. Wartime ink bottles were made in many different shapes and sizes, with caps made of metal or plastic, or even simple cork closures. One style of bottle that seems to be a common type has an integral rest for a pen. This is an old style, the oldest ones had simple openings closed with a cork and were made not only of glass but also from stoneware and ceramic. This shape appears to me to have been more popular in Germany (or at least in Europe) than in the USA, if surviving original bottles are a good indication. Here are two original bottles of this style, from Wehrmacht dumps.
These have screw-on plastic tops. They are different and probably are from two different brands of ink. They probably had labels originally, though no trace remains. Whether or not all ink bottles had labels on them at that time or not, I don’t know.
The company J. Herbin in France still produces ink in 30 ml bottles that are basically the same as the originals above. Here are two modern J. Herbin ink bottles with the labels removed. I put a pen on one so you can clearly see the pen rest feature these have. It’s a handy feature that keeps inky nibs off the desk.
J. Herbin ink in these 30 ml bottles is widely available from online retailers.