I don't know what those bolts are for, but they do not hold the keel on! The keel on the 23-2 is molded as part of the hull, no bolts. The lead ballast consists of lead blocks set into the inside bottom of the keel on both sides of the CB housing and set in a bed of thickened resin, then glassed over.. The Centerboard itself has about 15# of lead flashing inside to allow it to drop instead of floating. I wonder if maybe those rusty objects are what O'DAY used to lift the lead ballast into the boat? They look like they might be eyebolts that have been bent over.
I'd maybe give Rudy Nickerson a call at D&R Marine (508) 644-3001, he was the Parts Manager for O'DAY fro many years and now runs a little shop supplying parts for our "old" O'DAYs. He may know what the "bolts" might have been for. But,, they do not hold the keel on, so no danger of the keel falling off.