This is a specially produced glossy bookplate bearing the original signature of Luftwaffe fighter ace Schleinhege. Hermann Schleinhege (21 February 1916 – 11 March 2014) was a German Luftwaffe fighter ace with JG54 and recipient of the Knight's Cross of the Iron Cross during World War II. Schleinhege was credited with 97 aerial victories, all on the Eastern Front.
This is not an easy Luftwaffe signature to source at this price.