Hi Itchybird,
Vintage Whizzer tanks were made in two styles. The tanks used with the "H" motor [1946 to May 1948] had smooth sides, were pewter [silver]in clolor, and came with yellow decals. The tanks used on "J" and later vintage motors were embossed with the Whizzer logo and available in several colors, most popular was Whizzer red [Maroon]. All vintage tanks had the brackets brazed onto the tank and had both sides of the bracket with a curved design to fit the top bar on the bicycle frame.
The new edition tanks were also originally smooth sided, but the brackets were flat across the top to fit on a flat mount welded to the new edition frames. Later tanks hade the Whizzer logo embossed but still maintained the flat top mounting bracket. Just before production stopped the gas tank was offered in a larger version.
The vintage and new edition tanks held approx the same amount [5 quarts], however the rare larger tank was rated at 1.7 gallons. My Ambassador has the larger tank, but due to the mounting position it holds abount the same amount as the 1.2 gallon tank before it overflows.
Have fun,
