Marcian, AR heavy miliarense, 24mm, 6.07 g. Constantinople. AD 450.

DN MARCIANVS PF AVG, pearl-diademed, draped and cuirassed bust right.
GLORIA ROMANORVM, Emperor standing facing, looking left,
holding spear and shield. 

Star in left field.
Mintmark CON.

RIC 526; RSC 10Ba; MIRB 19; Sear 21387.
Extremely rare.

With permission of Numismatica Ars Classica, May 2004.
Sales history of this coin:
NAC -> Marc Poncin's collection, May 2004.
CNG Triton X, Lot 822, 9 Jan 2007.
Spink auction 8006, Lot 934, 26th March 2008.
Baldwin's auctions 62-63, Lot 131, 29 Sept. 2009. (Last known appearance)

One other example with a slightly different lower edge chip was sold as follows:
H. D. Rauch GmbH auction 75, Lot 979, 6. May 2005
H. D. Rauch GmbH Mail Bid Sale 10, Lot 872, 2nd March 2006.