Meanings of authenticate instance in English

I know of only one well- authenticated instance.

Is there any authenticated instance of a dog having recognized a full length picture of his master?

We have seen that there is no authenticated instance of a hybrid between the dog and the fox.

After a careful search for well- authenticated instances of burial, aquatic and semi-aquatic, but two have been found, which are here given.

Here is a well- authenticated instance which goes far to prove the truth of an assertion made to travellers in many parts of Africa.

Even on objects of the Bronze Age they are so rare that it is doubtful whether a single well- authenticated instance could be produced.

Universal belief, well- authenticated instances of their appearance to men, and of the fulfilment of prophecies and omens, are all evidences of their existence.

Mr. Farnsworth, who next addressed the House, gave numerous authenticated instances of outrages and murders perpetrated by rebels upon Union soldiers and citizens.

Authenticated instances are known of men getting ten, fifteen, twenty, and thirty thousand dollars within a week or ten days, without particularly hard work.

I may go further, and ask him for a well authenticated instance, where an emancipated slave, singly has imbrued his hands in his master's blood.