585-675 AD., Merovingian, Chitry-les-Mines mint (département Nièvre), moneyer Austrulfo, Tremissis, Belfort nrs. 1428-1429.

Merovingian, Chitry-les-Mines mint (département Nièvre), moneyer Austrulfo, ca. 585-675 AD.,
Tremissis (ø 11-12 mm / 1 g), gold,
Obv.: AVS[TR]ULFO , diademed bust right, legend around.
Rev.: CASTO[R]IACO , cross in a dotted circle, two dots in the second and in the fourth quarter, legend around.
Belfort's standard work of reference (1892-1895) under nrs 1428-1429 whilst Depeyrot (1998) adds a third specimen .

a find from the Oudenaarde region

thanks to Arent Pol (currently Leiden University, formerly Geldmuseum and the now defunct Royal Coin cabinet) who wrote on 12/09/2014:
"Many of the 7th-century tremisses of the Franks are quite unreadable, either because the flan was to small (in relation to the die) or because the die-cutters did a bad job in rendering the legends; this specimen seems to combine both "defects". And the design usually is not of much help either in the identification process, since the majority of these coins show a profile bust and a cross of some kind...
This recent find can be identified as struck in Chitry-les-Mines by the monetarius Austrulfo: the obverse reads AVSTRVLFO, the reverse CASTORIACO. From this mint (situated in the département Nièvre) up till now only six coins have come to light, two of which found their way into Belfort's standard work of reference (1892-1895) under nrs 1428-1429 whilst Depeyrot (1998) adds a third specimen. Of these six coins, five are of different varieties and without knowing the gold content not much more about its dating can be said than "c.585–c.675", the period of the so-called national phase of gold coinage. However, two out of six coins have been analysed and their rather base alloy hints at a rather late date of production, maybe c.650 (but this is quite speculative, and needs confirmation by analysis of the new item too!)"