This is a small porcelain cup produced in 1938 by Austrian factory Giessl & Czeika.

The factory specialized in products for hotels, restaurants and cafes. It was established in 1846. The cup is made of thick porcelain and seems to be designed exclusively for places where such products are in constant use. That's what would be served for soldier Svejk in a tavern.

Giessl & Czeika mark: