Large Machined Hole Above Oil Filter on '06 TSX -- Should there be something in / on it?

When doing my second oil change on our '06 TSX yesterday I noticed the just above the oil filter the block has a large machined and threaded hole of about 1" diameter. It shines like untouched aluminum. I am
wondering if something fell out of or off of there as it had not a bit of dirt in it even though the car has almost 7,000 miles on it now.
Is this just a mounting point for some option my car doesn't have?
Thanks for any clues!

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