harry potter - What are the ways of someone identifying him/herself at Gringotts?

We know by hand for two possible ways of how someone can identify himself as the owner of a vault in Gringotts.

The first one we know of, from the HP & PS were Harry goes to Gringotts with Hagrid and the second is giving Harry's vault key to the goblin.

Also, on the same scene we can see that another type of identification is with a "letter" (I am talking about the letter that Dumbledore gave to Hagrid in order him to extract the Philosopher's Stone) but I guess because it was Dumbledore asking that it was a "special" case and that wouldn't happen with normal people.

The third one we know is from HP & DH I-II at which point Harry, Ron & Hermione are going to Gringotts after using the Polyjuice potion and Hermione has the form of Bellatrix and the identification is being done by Bellatrix's wand.

What other known ways do we know of for "customers" identifying themselves to the Goblins in order to get access to their vaults?

Answer

Another way seems to be by appearance

When Harry goes to Gringotts shortly before beginning his second year, he is led to his vault by one of the bank employees, with no mention made of keys, letters, or wands, suggesting that the Gringotts goblins recognize some customers by their appearance, namely Harry and the Weasleys:

“Meet you back here,” Ron said to Hermione as the Weasleys and Harry were led off to their underground vaults by another Gringotts goblin.

—Harry Potter and the Chamber of Secrets

Similarly, Griphook and Hermione seem to have planned for Hermione to present no identification, relying on the fact that the Gringotts employees would recognize Bellatrix:

“You have . . . identification?” asked the goblin.

“Identification? I-I have never been asked for identification before!” said Hermione.

“They know!” whispered Griphook in Harry’s ear, “They must have been warned there might be an imposter!”

—Harry Potter and the Deathly Hallows

This is not so extraordinary. The magical population of Britain numbers in the tens of thousands at the highest. The goblins that work at Gringotts can recognize the key to a given vault (though that may be because of secret markings).

"Got it," said Hagrid at last, holding up a tiny golden key.

The goblin looked at it closely.

"That seems to be in order."

—Harry Potter and the Sorcerer's Stone

It certainly seems possible that they can remember the faces of all the people who do business with them.