Olds O-21 marching trombone

[AtomicClock]

I have an Olds marching trombone. I see references here and around the web referring to O-21, but I don't see a model engraved anywhere. Am I missing something?

[JohnL]

No, you're not missing anything. Most Olds horns don't have model numbers on them. We know the model was O-21 because that's the model number in the catalogs.

[AtomicClock]

Thanks.