I have an HBC for each of a few horns, and I was thinking I was going to mix them up, so I reached out to HBC on facebook asking about it.

Following is the response; hopefully someone else will also find it helpful. (paraphrased to remove personal details)

We've "labeled" each HBC and this has been achieved with grooves around the circumference.

1 Groove = Yamaha Pro/Neo,

2 Grooves = Besson English Edgware and German,

3 Groves = Adams, Boosey & Hawkes Sovereign/Imperial, Geneva, John Packer Current, Sterling Current, Willson and Wessex,

4 Grooves = Yamaha Custom, 5 Grooves = Yamaha 641 Vintage.

As you can see with the 3 Grooved HBCs, it would be impossible to engrave all the instrument options on, so we opted for groove coding. Groovy eh!