Previous owner drilled holes in it. I’ve tried searching “rv hose pass through” and variations of that.
It’s a marine part.
Smartmarine 6 inch Boat Hatch… https://www.amazon.com/dp/B09W8ZFFL5?ref=ppx_pop_mob_ap_share
Your image has a cool optic illusion. Look at the top 1/3 of the image while temporarily obscuring the bottom 2/3 and imagine you are looking at the end of a box with the hatch on the end of the box.
Glory hole?
Joke answers reply to this comment…
Radiation Stopper Plug
bung hole
Source: What is this cap thing called?
