Is this a Regal only device...my search seems to indicate this. How effective were they?

The new style brow was introduced in the Regal line in April of 1987. Coach 3418 had old style, by 3429 it was new style.

All the Breakaways and Regencies from about that point on used the new style as well.

My coach was built in July of 86 and was marketed as an 87 model. I refer to mine and all of those built in late 86 as 86 models since they have the old style. Early 87 models still had old style but were made in 87 so I think of them as "old style" 87s.

It supposedly keeps rain from running down the windshield. I suspect it is an advantage as the coaches age, less likely to leak in the top of the windshield?