Any clue what this flag/decoration is?

Guideon is clearly a Cavalry Troop Guide-On, from 1983 belonging to the U.S. 12th Cavalry. Anything more would have to come out of Army Heraldry in DC. I know for a fact that the Army, in The Pentagon's Library, has EVERY SHOULDER PATCH, MISSION PATCH, BRANCH PATCH AND UNIT PATCH on file there. An Inquiry to the Army's Public Information Office might be a good place to start given that They and the Library are about 4 Ring's from each other, and on the same floor.

12th US Cavalry
The 83 is year served

On 15 June 1983, the 1st Battalion, 12th Cavalry Regiment was relieved from assignment to the 1st Cavalry Division at Fort Hood, Texas. Reorganized in 92

Looks like a 1980's era enameled memento luggage tag. That was a thing then, I remember my dad having a handful of them from various meetings and conventions. I'm guessing that was a keepsake from a 1983 12th CAV reunion of some sorts, but they got the red/white reversed on the order. Hard to tell from the photo, but that strap sure looks like pleather so I'd think 1983 for sure. If the back of that has painted area with lines for writing your name and address, that's for sure what it is.

Enameled memento luggage tags were a thing in the 80's, I remember getting a lot at industry conventions. That looks like a luggage tag and I'd guess it's swag from a 1983 12th CAV reunion of some sorts. Guessing they got the red/white backwards on the order.

Just a thought but maybe take it to a military museum and let them look at it. Everyone thinks the '83 means 1983. The rest is unclear since the colors are wrong, but the museum should shed light on it. Maybe it was taken as a drought from some training exercise. Semper Fi brother!

I believe it is the 12th Marine Detachment from 1983 but not positive. Contact Medals of America. they have nearly every Medal that was ever issued and they can tell you what it is. Go to MedalsofAmerica.com on the computer and it should come up.