Hello, Mike!
I have the same set, which was also one of my early finds!
The Slant Erie era appears to have been a transition time period where I've seen a number of 'different' things, including differences in casting quality etc.
Since finding mine, I have seen others. I don't think the misspelling adds much, as far a valuation, unless for a person like me, that has decided that they like the odd ducks!