The Mint Birmingham, Specimen Piece Cent, c. 1870:

Obverse: THE MINT . BIRMINGHAM . , around the arms of Birmingham.
Reverse: SPECIMEN PIECE , curved above laurel wreath, CENT , in centre.
Edge: Plain. Weight: 19.86 grams. Diameter: 38.5mm.
Composition: Likely to be; 70% copper, 15% nickel, 15% zinc.

Surfaces with original lustre, uncirculated but with scuffs and an edge knock around 5 - 6 o'clock reverse, there is a flan flaw above the A in BIRMINGHAM.

This is the only example known to us.
Cf Sweeny ADV 21 / 22

Sold March 20