This may be a pretty common thing but I have never seen it before. I was parting out some trash picked bikes when I came across this
Looks like a skip tooth mixed with a regular chain ring. Is this common and I just never noticed before?
A 1st on me too and think it's not a 'skip tooth' although skipped it does not look as if it's correctly spaced for a traditional 'skip tooth' but skipped because, it looks like it's spaced to size of standard chain, and it's a missing teeth because it's an 'cheaped tooth' chain ring.
Albeit, maybe made that way because they thought it would transition easier like that.
The spacing of the teeth on a 1" chain is not identical to skipping a tooth on a 1/2" chain. People sometimes people cut teeth from a 1/2" rear cog which sort of works because it only engages over a short distance. Even if the tooth spacing would work, the difference in thickness would make a 1" pitch chain sloppy and would probably eat it in short order.