Delco Remy Horn - year/make?

[roysboystoys]

I'm tying to ID this horn. It's the first I've had without the cap on the end.

7 1/2" long

Has RD   and 16 on the end cap , marked 6 volt

Google frustrates me , I can't seem to find an ID source

I think it's Chevy , just before they changed the style to the rams horn.

Anybody recognize it or know I can look?

Thanks