Double-down is a stem variation or error that can be found on some Pez dispensers.
Normal Dispenser Stems
On a normal Pez dispenser, the word PEZ is written on one side with the letters "stacked" vertically, reading from top to bottom. On the opposite side, they are aligned to be read from the bottom to the top of the dispenser when it is held horizontally.
The Double-down Variation
On a double-down dispenser, the "PEZ" on the horizontal side can be read from the top to the bottom of the dispenser when it is held horizontally. In a double-down dispenser, the Z of the word "PEZ" is at the bottom of the dispenser on both sides.
Double-down dispensers appear to have been produced in the late 1970's and early 1980's, though a specific time period has yet to be established.
The appearance of double-down stems seems to coincide with the appearance of thin feet on Pez dispensers.
Patents & Countries
Double-down stems seem to be limited to dispensers with the 3.9 patent. They have been noted on dispensers made in China, Hong Kong and others with No Country name on the stem.
The double-down stem does not appear to be limited to a specific color of stem.