Venetian Coin Struck In Genoa?

I have been wading through Norwich's 'a history of Venice" one paragraph has me really intrigued:

Page 179 "........in retaliation the Venetian Domenico Schiavo......penetrated into the inner harbour of Genoa with three galleys and, as a final insult, actually minted some Venetian coins there before retiring"

The coins aren't identified and neither is the date reported. From the general context I assume the incident occurred in the 1290's perhaps the 1280's. Can any one provide any further information?