For your consideration, I offer a patent dated 1880s oval fitter rim chimney.
The chimney will fit a no. 1 size Pinafore burner. It measures 2 7/16 inches o.d. x 1 11/16 inches o.d. The chimney has flat sides The wide side
measures approximately 3 7/8 inches o.d. at the widest part of the bulge and the flat side is 1 5/8 inches o.d. The flat side is slightly concave in the
center. This is the way they were factory made.
There is a molded patent date in the glass near the bottom rim: "Pat. Mar. 30, '80. Top and bottom rims
are factory rough ground. You can see the two mold lines in one of the pictures. The glass has good clarity with no chips or cracks.