Bronze Portlights with Stainless Exterior Trim Rings?

Like all of the earlier tugs, at least through #42, Hull #20 has bronze port lights in the stateroom, head and shower. The port light's trim rings, on the outside of the hull, are stainless steel. Strange that a bronze port light would have a stainless trim ring. Was this done by the yard to match the stainless of the other windows (the five wood pilothouse window frames excluded)? Did the earliest tugs have bronze trim rings? Did the yard make the stainless trim rings? 

12 July 2013 update: Bob Allnutt, Victory #2, just confirmed that his stateroom, head, and shower port light exterior trim rings are bronze.