that tank is a West Coast Choppers bicycle tank (you have to weld all the seams and install a cap/bung and a petcock)
yes, that is exactly what it is. I actually used silver solder to seal all the holes and seams. I did not weld in a bung for a gas cap, I am using an oil fill cap from a valve cover and it has a rubber plug on the back. I cut the hole for the gas cap and the rubber just pushes into the hole sealing it tight.
I added 2 fuel line outlet tubes made out of copper tubing, silver soldered into holes in the sides of the tank at the rear. I am using an in-line shut off valve because it was much easier than trying to put a screw in petcock into the tank. Besides that, i was able to hide the in-line shut off valve for a cleaner look.
You also have to pressure test the tank to check for leaks once the welding/soldering is done. yes, it is safe to use silver solder to seal a gas tank, but it has to be silver solder and you must use acid flux and a propane torch to do it right.
you have to make a mount that isn't ugly, so i made a hidden mount under the tank. This mount allows the tank to be mounted to the frame very securly, and it also allows me to remove the tank in about 20 seconds if i need to.
I also ground down the welds on the front of the tank, filled the area with bondo, slightly re-contoured and smoothed the front of the tank. Paint is metallic black laquer with clear laquer over it.
There is a lot of work in making one of these tanks actually capable of holding gas, so if you can't weld, braze, solder with a torch, do body work and paint, i would not attempt it.
the tanks are made out of some heavy gauge steel, they are not tin, and they are not flimsy at all. they are much thicker and stronger than the kit supplied gas tanks. I picked mine up for $7.00 off e-bay.
here's another west coast chopper tank that i did. this one is on a non motorized bike, so i didn't bother welding it all closed. I just ground down the welds on the front, filled the area with bondo and smoothed the front of the tank. I did cut a hole and put in a more realistic looking gas cap, and it's the same style as the one i used on the above tank. paint on this one is metallic orange laquer, with clear laquer over it.