My '79 23 Sceptre came with Attwood Louvers.
http://www.attwoodmarine.com/store/p...-Louvered-Vent
They were "chrome plated" originally but over the years turned into a dull gray color with a little "chrome" left over.
After looking up what they cost new (
), I painted them the hull color (Jade Mist), reinstalled them and called it good.