Why does he throw "three or four gold pieces on the threshold"?

I remember him as if it were yesterday, as he came plodding to the inn door, his sea-chest following behind him in a hand-barrow—a tall, strong, heavy, nut-brown man, his tarry pigtail falling over the shoulder of his soiled blue coat, his hands ragged and scarred, with black, broken nails, and the sabre cut across one cheek, a dirty, livid white. I remember him looking round the cove and whistling to himself as he did so, and then breaking out in that old sea-song that he sang so often afterwards:

“Fifteen men on the dead man’s chest— Yo-ho-ho, and a bottle of rum!”

in the high, old tottering voice that seemed to have been tuned and broken at the capstan bars. Then he rapped on the door with a bit of stick like a handspike that he carried, and when my father appeared, called roughly for a glass of rum. This, when it was brought to him, he drank slowly, like a connoisseur, lingering on the taste and still looking about him at the cliffs and up at our signboard.

“This is a handy cove,” says he at length; “and a pleasant sittyated grog-shop. Much company, mate?”

My father told him no, very little company, the more was the pity.

“Well, then,” said he, “this is the berth for me. I’ll stay here a bit,” he continued. “I’m a plain man; rum and bacon and eggs is what I want, and that head up there for to watch ships off. What you mought call me? You mought call me captain. Oh, I see what you’re at—there”; and he threw down three or four gold pieces on the threshold. “You can tell me when I’ve worked through that,” says he, looking as fierce as a commander.