Are street blades with bottom-center address tabs an old design?
Yes, they are. They were very commonly used in Southern California starting in the 1950s, with new installs being done into the early '70s.
The most common ones were dark blue with white lettering, but there were many different color combinations used by various municipalities, especially in Orange County. Some even had the city name in very small lettering so you'd know which suburb you were in.
Sure, they were hard to read at night, but they gave some personality to suburbia. Oh, well...