This image has been mirrored to match conventional celestial maps. It was
then digitally rotated one degree CCW with respect to the mirrored original(1), to
align it properly with true north and to match it with van Maanen's M33 image(2).
The faint bleedthrough image, from the reverse side of this scanned page, depicts the galactic distribution of dark nebulae.
Lundmark employed the same comparison stars and plates as van Maanen. (The author does not have a copy of Lundmark's data table, and assumes that he used a print of Ritchey's 1910 plate for the annotated photo above.)
(1) Lundmark, Knut, "Studies of Anagalactic Nebulae," Nova Acta Regiae Societatis Scientiarum Upsaliensis, Volumen Extra Ordinem Editum 1927, Plate III. (Thanks to William Keel for kindly furnishing a copy of this article.)
(2) van Maanen, Adriaan, "Investigations on Proper Motion - Tenth Paper: Internal Motion in the Spiral Nebula Messier 33, N.G.C. 598" - ApJ 57, 264-278, (1923), Plate XV. - NADS