Considering his 'emotional attachment' to it, I would be surprised if he passed it off at all, or at least not so quickly. Once passed off, there is a good chance it would eventually wind up in the church or buried under some Wizard's sub-basement.
There are 30 coins, plenty for Nick to choose from.

But Nick *doesn't* have the others to choose from for elevating new henchmen.  Tessa and Rosanna made off with the bag containing most of the loose ones at the end of Small Favour, so Nic had to resort to retrieving Ursiel and Lasciel to rebuild his cadre from Death Masks.  Unless he went to extraordinary lengths to rescue them in the few minutes the escape from Hades took, those two coins are lost to him again for the long term.  Even if Saluriel (Cassius' Fallen) and most of the others in Church custody get busted out soon, Nic is a pariah with a price on his head - rolling with Tessa and Imariel for the next few decades is going to look a lot better to most of them.

Deirdre's Fallen might be the only one willing to take Nic's calls at this point.

I really do want to see some silver buried under a wizard's creepy prison-fortress island at some point, though.

Doesn't the last Starborn predate Mab being in her position though?  When was the Last Starborn active, about a thousand years ago?  And Mab has been WQ since Hastings, was it?  Which is maybe a thousand years ago, but it's also off by 5%.  And that assumes that she jumps right into it immediately.

We don't actually know that Mab started the gig exactly in 1066.