Here is very small square-shaped ink with very rounded corners and shoulders and a simple flare lip. The bottom has a sand chip type pontil scar. This doesn't look American, but I can't be sure.
Unembossed
Height: 1 7/8"
Color: deep apple-olive green
Condition: near mint - structurally perfect and clean, just trace ink residue in one corner.
Reference Number: UN60
Price: $40