Hi Melanie and welcome
This is quite the coincidence - I had the same question from someone who found a fragment of one of these bottles recently.
The bottle was made for the J.A. Gilka Company in Berlin. It contains a liqueur called "kummel" which is a sweet alcoholic drink flavored with caraway seed, cumin and fennel. It reminds me of the traditional bitters which is made from an herbal infusion in alcohol.
Gilka Kummel is still made today.
Here is a link to the wikipedia page for kummel and to the German wikipedia page for the Gilka company.
Below is a picture of a circa 1966 Gilka bottle from the Master of Malt website. The current bottle has been modernized somewhat but has a similar feel.