The scientific and historical approach is valid. The historical measurement series are among the oldest sistematic observations of the geomagnetic field which provide relevant information regarding its   long-term evolution.

The paper presents a lot of old documents, sketches, not adequately inventoried until now. This should be a considerable benefit  in rescuing the history of Potsdam Observatory before these facts may be lost.

A lot of geoscientists involved in running the observatory, especially Adolf Schmidt,  were pioneering scientists in geomagnetism and their work is of great importance today.  

Bottom of the line, the theme of the manuscript is valuable,  relevant  and of interest to the geomagnetic community. It is correctly structured and written, without repetition of ideas or lack of elements.

Some of the minor technical corrections I propose are in the captions of the figures:

Page 11, Fig. 1. ..Hellmann, 1912 .remove Fig. 19

Page 11, Fig. 2. ....Hellmann, 1912 remove Fig. 20

Page 12, Fig. 3. .....Hellmann, 1912 remove Fig. 23

Page 13, Fig. 5. .......Left: remove the second : and .... Hellmann, 1912 remove Fig. 25

Page 13, Fig. 6. .....Hellmann, 1912 remove Fig. 21

Page 14, Fig. 7. .....Hellmann, 1912 remove Fig. 22

Page 14, Fig. 8. .....Bock, 1928 remove Fig. 1

General comments

This was nice to read this manuscript. The paper is well written and easy to follow. The article is really interesting, especially for people having something to do with observations of earth's magnetic field.

This paper presents a history of geomagnetic observations in Potsdam which are currently continued by Niemegk Observatory. However, in the introduction, we can find some interesting information about earlier observations in Berlin, which are conducted in the frame of the Göttingen Magnetic Union.

Most valuable in the paper is describing problems and difficulties experienced by people engaged in establishing observatory and good-quality observations. This makes us realize that it is not easy, even if are involved in working with such brilliant people, as described in this article.

Also valuable is that the article familiarizes readers with an affiliation and directors of the Potsdam Observatory, as well as instruments makers. Archival figures is also strong point of the publication.

To conclude, I can say that the author has done a good job, reached many archival materials, and arranged them into a logical and ordered whole.

Specific comments

Page 4, line 18                                  It would be good to add some reference concerning oscillation boxes

I would recommend to add DOI’s in Reference section where it is possible, eg.

Page 9, line 2-4                                 https://doi.org/10.1029/97JB01423

Page 10, line 13-14                          https://doi.org/10.1556/AGeod.37.2002.4.8

Page 10, line 15-16                          https://doi.org/10.1029/2000RG000097

Technical corrections

Page 7, line 17                                  should be Potsdam

Page 1, lines 23,24,25,27              I would suggest uniformly Gauss or Gauß