What did the emperor of Blufescu give Gulliver before departure?What convinced the ship's captain about the Gulliver's story?

From the text:

I lay down on my face to kiss his hand, which he very graciously gave me: so did the empress and young princes of the blood.  His majesty presented me with fifty purses of two hundred sprugs a-piece, together with his picture at full length, which I put immediately into one of my gloves, to keep it from being hurt.  The ceremonies at my departure were too many to trouble the reader with at this time.

I stored the boat with the carcases of a hundred oxen, and three hundred sheep, with bread and drink proportionable, and as much meat ready dressed as four hundred cooks could provide.  I took with me six cows and two bulls alive, with as many ewes and rams, intending to carry them into my own country, and propagate the breed.  And to feed them on board, I had a good bundle of hay, and a bag of corn.  I would gladly have taken a dozen of the natives, but this was a thing the emperor would by no means permit; and, besides a diligent search into my pockets, his majesty engaged my honour “not to carry away any of his subjects, although with their own consent and desire.”

Gulliver convinces the captain of his story by taking removing the items he carried homeward from his pocket.

We were now in the latitude of 30 degrees south; there were about fifty men in the ship; and here I met an old comrade of mine, one Peter Williams, who gave me a good character to the captain.  This gentleman treated me with kindness, and desired I would let him know what place I came from last, and whither I was bound; which I did in a few words, but he thought I was raving, and that the dangers I underwent had disturbed my head; whereupon I took my black cattle and sheep out of my pocket, which, after great astonishment, clearly convinced him of my veracity.  I then showed him the gold given me by the emperor of Blefuscu, together with his majesty’s picture at full length, and some other rarities of that country.  I gave him two purses of two hundreds sprugs each, and promised, when we arrived in England, to make him a present of a cow and a sheep big with young.