Terry,
Your aluminum popover pan could have been made by Griswold if they did make ERIE popoevers in aluminum. The other possibility would be that it was made by someone else by copying an ERIE iron popover pan in aluminum. Almost always Griswold used different pattern numbers for their aluminum items than those made in iron but there can always be exceptions and, I think, in the very early days, the pattern number system had not been finalized. Perhaps some aluminum was made with the iron pattern numbers. Griswold did make some aluminum pieces in the early 1890's marked ERIE ALUMINUM or just ERIE like some teakettles. They are scarce.
My point, though, is that your piece may be a copy casting. Can't tell without seeing or comparing its size with that of an iron piece. I would think that the iron and aluminum items would measure very closely but a copy in aluminum would be noticeably smaller than the original.
Steve