Probably the Grand Opening ad
This July 13, 1950 ad, the first mention I could find of the “Sky Vu”, has a description of the drive-in that isn’t repeated in its future ads in the weekly Elizabethville Echo. It’s possible that the drive-in opened a few days earlier or that this was the first time it thought to advertise in a town 10 miles away, but this strongly suggests that the Sky Vu opened in July 1950.
I have no copyright interest in this advertisement, and its bare copy is unlikely to have been renewed, but don’t take my word for it. I have uploaded it here for the scholarly fair use of attempting to establish the (otherwise unknown?) opening date for this drive-in.
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