The #500 Octagon pattern was made 1928-1935 and 1955-1957. The frozen dessert was made in crystal, moongleam (shown) and flamingo. there is another Octagon pattern, #1229 (the "Octagon" name was coined by researchers in both lines).
Several companies made similar dishes. Heisey's dish of this type is usually not marked but there is a rectangular thumbprint in the bottom ot their dishes.
Information for this listing was found in "The Collector's Encyclopedia of Heisey Glass 1925 - 1938" by Bredehoft.
See Cambridge #1110 for their example of this type of dish.
