Is It a Throwback?

All upper-case sign, with button reflectors, on southbound Interstate 680 in Solano County, California

The Parish Road exit from southbound Interstate 680 in Solano County has button reflectors and no lower-case letters. Either it's a long-standing error or it's a very old sign. The advance sign for the exit also uses button reflectors with no lower-case letters.

This photo was taken in July 2009.