I'm not sure how accurate that dating is. I've owned a half dozen Morgan vises and they were all "Chicago". I doubt they were ALL pre-1947. If all the Morgans built 1947-1970 were "Aurora" (especially since I live only a few miles from the original Aurora factory), why would I NEVER see one?
Basically, I think that most Morgans still read "Chicago" up until the move to Milwaukee. I can't say it definitively, but I can't explain how a factory in my own backyard would not have craploads of their vises in all the local shops.
Those are the years when Morgan was located in those places.
That portion is accurate, at least to with a few months or years at either end of the date ranges.
Whether or not they changed the wording on the products to reflect that is a valid point, and I've rarely seen Aurora marked Morgans myself, but we do know Aurora-marked Morgans exist.
The vast majority of Morgan vises I've seen have been marked "Morgan Chicago" yet they were only located in Chicago for about 18 years. Then for about 23 years in Aurora, and now owned by Milwaukee Tool and Equipment Co. for about 44 years, more than the other 2 locations combined, yet still, at least from my own experience, "Morgan Milwaukee" marked vises aren't as commonly seen as "Morgan Chicago" marked vises.
It may be safe to assume that Morgan was more prolific in the pre-1947 or "Morgan Chicago" era, which included WWII when they probably made a lot of vises for the government, and a lot of those vises have found their way into the used marketplace in recent years.
I've asked the Milwaukee Tool and Equipment people about details like that in the past, and I think they really don't know the answers themselves. They've also been less than accurate (or less than interested) about certain historical details on the vises themselves, like when (or if) thrust washers were used on the screws, and when certain styles of pins were used to hold the jaw inserts; i.e., type A groove pins vs their current use of spring pins or roll pins.
And while on the subject of such **** details, it's been oft-repeated on internet forums, and on the Milwaukee Tool and Equipment website, that Morgan vises have (always) been painted (some government spec.) blue, or words to that effect, and while that may be true for Morgan vises made by Milwaukee Tool and Equipment Co., it isn't true for older Morgan vises, especially Morgan Chicago marked vises, which were originally a flat black or charcoal color, not blue.
