Heraclius. 610-641 AD. AV Light Weight Solidus of 23 Siliquae (4.29 g). Struck 610-613 AD. Thessalonica mint? 

d N hERACLI US P P AVI (blundered legends), helmeted facing bust holding cross.
VICTORIA AVCC, cross potent on three steps; IE/C+N+B. 

Cf. Adelson NNM 138, 180-183 (Tiberius II and Maurice Tiberius); MIB III 81.3 (same style dies but no crosses); cf. Wroth pg. 155, 
276 (Maurice, Ravenna); SB 822. (no crosses in exergue). 

Apparently unpublished. 
Adelson lists four (unillustrated) specimens with this mintmark, but for other rulers, cited in the 19th century, and one is included in Wroth's BMC Byzantine. 
MIB III 81.3 is likely a die match. Apparently normal solidus dies were subsequently altered. If Hahn's attribution of 81.3 to Thessalonica is correct, then the entire C+N+B coinage may be from there.

With permission of cngcoins.com, auction 61, Lot: 2236, Sept 2002.