I disagree with this a little bit, always check the edit history, TOC's are extremely often on the wrong release (especially older releases). A lot of people get lazy and just add the TOC to whatever release they can find, instead of adding their own specific version to MB.
Other people will say to play it safe, but personally I think that if there's little unique data on a release that helps you identify it/ figure out if it's real, then there's zero loss if you merge it into one you know is correct. Someone can always add their version again.
But again, always check the edit history, leave notes asking for info from the original editors, and try track it down yourself.
After that... I merge. If I can't identify it, nobody else can, and it will literally be there forever (as you can't prove that something doesn't exist).
But as a rule of thumb, if you're even slightly unsure, just leave it.
And add whatever release (physical or digital) as well as you can, that's all you really have to worry about. Even if it possibly duplicates data.
edit: as Freso says, it's much easier to merge than split, so if you're unsure, duplicate that info!