I've recently aquired an 8D..

Serial number 5-560***

I was told that it was made around '86.. But when I check serial charts it's totally opposite. I find it telling me '57ish.
I've also seen some where in the 80's you add 50 to the serial prefix, but wouldn't that just give '55?.

Do the 8D's from the 50's have the mechanical trigger aposed to the strung, and the 2nd valve ringe directly solderd on aposed to the brace going around the turn of the crook?

The horn is in amazing condition if it's a '55/'57!

Serial numbers from the 1950's have six numbers in a row with no spaces and no hyphens. There are no prefixes on horn this old.

A 5(hyphen)six digit number is from after 2000.

The formula you heard about where you add 50 to the prefix only applies to 2-digit prefixes.

I hopes this helps you.

So where would this leave me?

My horn doesn't fit in to any of these catagories. The prefix has no hyphen, just a space.

Okay, 5 (hyphen) or 5 (space) means it was made after the year 2000.