So, what did I WIN? I don't want the hubcap! lol!
Initially, I thought it was an aftermarket Wire cover for the very reasons you said...they were the same for all Big 3 companies.
I worked in a salvage yard in the 70's-80's at various times had to identify or find a single wheel cover or a full set for somebody. If it didn't match the Hollander, it was aftermarket, plain & simple. As you found out, and so did I, if you changed out the centers you could build one or a few to suit a request. Sometimes in a junkyard request, the customer would have a damaged one we could salvage out the center from, other times we would scab one off a 15 inch cap for a 14 inch request and so on. Sometimes, we would build a set of 4 out of various parts & pieces. In the day, lifting wire wheel covers was a very commom theft. Enter the Locking Hubcaps of the later 70-80's cars.
Who knew???
Well, I did! I was hoping to see other input to help confirm what I recalled already. This is a case of what I would have considered "Useless Knowledge" ...until this post.
Richard