Shonuff8 t1_j2bf2d0 wrote
Reply to comment by hipoetry in Mystery WMATA/Metro survey markers: Can any intrepid city planners or engineers explain what these discs are (or were) used for? I seem them all over the place, even sometimes away from Metro stops. by LilGeographersRoom
Can confirm, have seen some of the sewer manholes stamped with 1880-90 dates around the Navy Yard area.
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