OK, as far as I can tell from the Perfect Tank Display that I have, a #6 is 3/4 ounce. Then they jump up to a #12 which is 2 1/2 ounces. It doesn't look like they made a rectangle tank in a anything from 1 ounce to the 2 1/2 size. I have three of the #6 tanks, one new in box and two used, and I have four of the #12 tanks, all four new but only two in correct boxes. Let me know if these interest you or PM me an email address or cell number I send some pictures to.
Type at you later,
Dan McEntee