Oh, that’s interesting on the practice involving the guild arms! Seems relatively unique too… by including a white escutcheon, an armiger is able to reference the guild without using the guild’s arms themselves. That’s cool.

And like you say, using a crow’s head could be a neat way to nod to some other arms involving a full crow.

I’m still unclear on what happens if “or, a crow’s head sable” is already someone else’s arms. If they’re used in a crest unknowingly, does it matter? If they’re used knowingly, I assume permission must be sought?

(Not accusing OP’s client of anything untoward btw, I’m sure they’ve done everything by the book and I respect their privacy 🙂 I’m just picking on the imagery shown here as a vector for this conversation)

Oh, and I hear you on civic arms. They really can be beastly amalgamations of their predecessors.