We have a Cast Iron Salvaged Base Vintage item.  It is completly rusted.  There are fluted lines along the upright outside sides and a design around the center as well.  It measures about 3 3/4" square x about 1 1/8" in H.  The center large opening is about 2" across with the small inside opening being about 3/8" across.  This may have belonged to a ?lamp? at one point, I'm not sure.

Lamp Base Cast Iron Salvaged Vintage