Hans:
NuTone was Sears' provider for some of its range hoods in those days, and the Kenmore versions, at least, had optional scalloped trim that you could pay extra for. The trim piece was held in place by the rolled-under rim of the range hood, plus some small screws on the underside.
We had a Kenmore hood in the non-powered version, in the anodized copper finish, with the scalloped trim kit. Non-powered hoods were kind of popular then, to go with through-the-wall fans installed over a range. The hood kept vapors and grease from billowing everywhere, helping funnel them into the fan's vortex. Our fan was a NuTone, and I'd give my left nevermind to have one today. The combination of fan and non-powered hood was very easy to clean.
Anyway, if you keep your eyes open, who knows? The scalloped trim for your hood might turn up - you're so lucky at finding stuff!