I have a mystery wiper arm. A regular Camaro coupe is on the top, the mystery one is on the bottom. They are both the same length and fit the same on the wiper hub. The only difference is the length of the riveted part and the hub end is shiny, not dull. I figure the shiny end means it's a 68 or earlier, due to the laws about chrome in front of the driver.

Anyone have any ideas? TIA
http://www.fototime.com/A5CC44E34C66F94/standard.jpg