Please help to decode this diff tag

this diff tag is on my 1980 f-150 Custom, 4.9l inline 6 cylinder, 4 wheel drive 4 speed manual transmission.
I think there is another number hiding behind the bolt, I am interested in the diff gear ratio and other info on the tag, thank you very much.

From what I see it's a 9" rear, and most likely a 3.50 ratio open differential.   As for the rest:

https://www.diyford.com/ford-axle-history-identification-ford-differentials/

You'll have to scroll down, and I'm not 100% sure on their take for dating it.  One I was just trying to decode last night came out as being built on July 4th, 1973.  I find it hard to believe that any car manufacturer would be assembling differentials on July 4th, at least in the U.S.  "Fordification.com" is another site that shows codes as well.

Nice truck!

Thank you very much, I was pretty sure it would be 3.50 gear ratio and the date fits Aug 4th 1980. I bought it in September of 1980.
The link was really interesting.

Yep 3:50 gears.
If it was limited slip you would see the L before '50'

3 L 50