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USC&GS NM instead of USC&GS BM?

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I found the mark below yesterday. It is a USC&GS chiseled square but I am trying to figure out the abbreviation around the mark. Any ideas what "N M" would stand for? I am not positive about the "U S C & G S" letters but it definitely has an "N" and an "M" on the bottom. (And there might be a letter or symbol between them).








Links to mark:

GW0645 - geocaching

GW0645 - NGS

Edited by TillaMurphs

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I see that GW0679 & GW0704 in that area are also chiseled squares. I don't believe that this level run is in Special Publication #18 (the only hypsometry link that I could find to download today), but maybe a local could come up with a description sheet from another source. MEL

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I suspect this is a magnetic station, actually one of a pair that would have been originally set. The inscription NM would stand for North Meridian. It's very typical of the type set by the US Coast & Geodetic Survey during the late 1890 to early 1900s. Regrettably some of the USC&GS Special Publications that described magnetic observations from the 19teens are not available on the NOAA library site.

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Foxtrot Xray - thanks for the guesses! :)


Mike - thanks for the idea of checking others in the run.


Mr. Doyle - thanks for the answer! I guess that explains the hole in the top. I will see what I can do to possibly find a USGS pub discussing this. I had spent quite a few hours searching through the online Special Publications before I posted my question and came up empty. However, my search was mainly looking for any (online) pubs obviously mentioning Virginia.

Now that you have narrowed the timeframe and mentioned that it is likely a magnetic station I will see what I can find.



After looking a bit more I searched through the following Special Publications listing magnetic observations and found quite a few in Virginia. However, I did not find the one at the Nelson County Courthouse in Lovingston, Virginia.

Special Publication 9 (1910)

Special Publication 15 (1912)

Special Publication 20 (1913)

Special Publication 25 (1914)

Special Publication 33&36 (1915)

Special Publication 42 (1916)

Special Publication 51 (1917)


Special Pubs 55 and 64 for 1918 and 1919 are not online and I can't seem to find any information before 1910.



Thank you.

Edited by TillaMurphs

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