The problems here come from Geometrische Wiederholungs und Denkaufgaben by Paul Eigenmann (Ernst Klett Verlag, Stuttgart, 1964). This book is rather difficult to obtain outside of Germany: the only copy I located near me is at the University of Illinois Urbana-Champaign library. I was introduced to these problems by a paper xerox copy credited to Peter Genta (Carlinville High School, Carlinville, IL, 1988). I started re-creating the problems in GeoGebra and rendering them as PNG. The original notebooks for most of these can be found at the tech page. I will update this gallery as re-create more of these. The numbering in the filenames comes from the original source. (I would re-post scans of the original source, but I am concerned about copyright — at least if I re-create them in GeoGebra, as I understand it, the images are my own to redistribute.)
There are a total of 176 problems. They are put into 4 groups by Eigenmann:
Group 1: Numbers 1-48: Angles in triangles, Symmetry, Areas of triangles and quadrilaterals
Group 2: Numbers 49-96: Circles and Pythagorean Theorem
Group 3: Numbers 97-144: Similarity, Proportionality, Heron’s Formula
Group 4: Numbers 145-176: Application of Algebra & Equations
The Ambling Pilgrim 