What does "see" mean in this context?

Question

   "Wizards have banks?"
   "Just the one. Gringotts. Run by goblins."
   Harry dropped the bit of sausage he was holding.
   "Goblins?"
   "Yeah –– so yeh'd be mad ter try an' rob it, I'll tell yeh that. Never mess with goblins, Harry. Gringotts is the safest place in the world fer anything yeh want ter keep safe –– 'cept maybe Hogwarts. As a matter o' fact, I gotta visit Gringotts anyway. Fer Dumbledore. Hogwarts business." Hagrid drew himself up proudly. "He usually gets me ter do important stuff fer him. Fetchin' you gettin' things from Gringotts - knows he can trust me, see.
. . . . . .

   "Why would you be mad to try and rob Gringotts?" Harry asked.
   "Spells –– enchantments," said Hagrid, unfolding his newspaper as he spoke. "They say there's dragons guardin' the highsecurity vaults. And then yeh gotta find yer way –– Gringotts is hundreds of miles under London, see. Deep under the Underground. Yeh'd die of hunger tryin' ter get out, even if yeh did manage ter get yer hands on summat."
(Harry Potter and the Sorcerer's Stone)

What does see mean?
Are they spoken English, “used for making sure that someone is paying attention to what you are saying and that” (MacMillan; but here’s no question mark in the example); abbreviated forms of “you’ll see”; imperative?

Answer 1

I think MacMillan in correct in stating that it's a rhetorical way of saying "are you following me?" or "do you understand?" It's a shorter form of "do you see?", sometimes also shortened as 'd'y'see?', or 'you see?'.

As a result, I do think there's a good case for saying that the publisher should have ended by both sentences with a question mark, although it's a somewhat pedantic point. It's certainly possible to say 'see?' at the end of a sentence, without expecting that the person being spoken to will actually respond. So @snailboat is also right in that it also acts as something like a discourse marker, in the same way as 'upspeak' (the practice of ending a statement on an upward note, as if asking a question) is way of seeking approval (often tacit), or softening the impact of a statement, rather than an actual question requiring a response.

Another way to think of it is as an equivalent of commands which are phrased as questions. When somebody says "would you pass the salt?" or (to the chagrin of parents everywhere) "can you pass the salt?", they are phrased as questions (and written with question marks), even though they are very commonly stated with the authority and intonation of commands.