My wife told me...........

All of my examples are flat bottomed and polished.... The shape of the fins is a little different on each example, and likely just varied with artistic preference for the individual making the piece..... They are great vases, and one of my favorites. On all of mine, the fins (flanges for Max

) are Uranium glass and glow like crazy. That just happens to be a requirement to be placed with the group in the first pic..... Red/Orange color with a brightly glowing Uranium glass content also..... Likely my favorite grouping of glass in the house, and the one that gets more compliments from guests than any other thing in the house......
Michelle was kind enough to put one of mine on ebay, allowing me the opportunity to add a great example to the group. (the far left example of the GF pieces) Three flanges, Raspberry interior, and the nicest of the 3 GF pieces....
Craig