busterbill wrote:
Could it be residue from the O ring. I assume Burkes are still made with an O ring inside. I'd just email Michael Burke. It is interesting. My Burke is older and I believe the design changed a bit. But it is also off in another state with my son or I'd take mine apart and see if it looks the same.
Here is Michael Burke's response regarding the mark.
"Hi Matthew,
I do not know what that black stuff is. It is not going to affect playability and it is not visible, but if you want to get rid of it, you could clean all the greae off and then wipe it with a rag or swab soaked in acetone. Alcohol might also work. Dry it off afterward and relubricate.
By the way- vaseline is ok in a pinch but it can build up and need to be cleaned off, so I recommend a synthetic food grade grease called Super Lube.
You can get a 3 oz tube at Amazon and it will last a lifetime.
Here is a picture of it.
All the best
Mike
https://www.amazon.com/Super-Lube-21030 ... 169&sr=8-3"