"Wehrstammbuch" Kriegsmarine register to Leutnant Wilhelm Gercken serving on U25 and U102 in WWI. Issued on 7. March 1938. The register contains a long list of his Navy service from 15. March 1906 until 10. January 1944. Including an entry of his service with 1. U-Boot-Lehrdivision Pillau during WWII from 1. October 1940 until 11. June 1942.
A period time book "U-Boots-Taten" by Fritz Otto Busch. Published in 1934. Furthermore two period time photocopies.
