Surprise!
It turns out that my initial thought was correct that Eureka made two versions of the 1447 (and likely the 1457, too)—the model number was reissued. So, now I wonder what the difference was between the second version 1447-A and 1447-B as both appear to be cosmetically the same, both have the gold-painted Disturbulator, and the ratings plates reveal no changes. Note that Eureka at this time was including the production time in its serial numbers (1447-A made during the 20th week of 1989, and 1447-B in the 7th week of 1990).
Here's a FB photo of a model-type 1447-A from 1989, its ratings sticker, and the 1447-B's rating sticker from an eBay listing:
[ATTACH=full]164682[/ATTACH]
[ATTACH=full]164683[/ATTACH]
[ATTACH=full]164684[/ATTACH]