This large-format series covered five subject areas, geology being one of them. The other areas were B. Botany, C. Zoology, D. Anthropology, and E. historical documents on the country and its inhabitants.
As was usual at the time, earlier volumes in this series were printed on large sheets of paper which were then folded twice and were not cut, leaving the pages unopened. This collection of unbound sheets was put in a thin cardboard folder, which is how we receive these books from the publisher and how you will receive them when buying them (please note that this is not a production defect). Back then it was common for institutes and libraries buying these pulications to cut and bind them themselves. Later parts were pre-bound as paperbacks.