OK, the old classic, Camptown Races has the line (depending on version):
“Went/going down there/town/South with my hat caved in”
Any idea what this expression meant? Google came up dry, and I don’t have access to D.A.R.E, so I turn to the dopers - once we nail this one, we can then move to the next line, the one regarding a “pocket full of tin”! Won’t that be fun 
I probably won’t be enlightening you much by noting that a “hat caved in” isn’t necessarily recondite imagery - it sounds a lot like a tired old hat that the wearer can’t afford to replace. And a “pocket full of tin” is money, possibly won via a bet on the bob-tailed nag.
Doo dah.
Some felt hats were/are undented when new. Nowadays, most fedoras and homburgs are sold with the crown pre dented, some even with the “grab dents” in the front sides. You can still get some cowboy hats with a domed crown.
The connotation is that the singer went to the Camptown Races with plenty of money, “a pocket full of tin,” and went home broke, “with my hat caved in.”
My wife an I, on our way out to California from Iowa in 1950, stopped in Baker for gasoline. Baker is between Las Vegas and Los Angeles. While we were at the gas station a fancy convertible pulled in for fuel. The occupants scounged around in pockets and purses and managed to come up with five or six dollars which, with gas at 35 cents a gallon, was enough to get them home.