The gubbins on Al McKibbon's headstock

[fergs40]

Hallo, upright people. I have never even picked up a double bass, much less played one, so please forgive that this question is coming from a place of complete ignorance...

 

I've been listening to Miles Davis' Birth of the Cool this morning, which features Al McKibbon on several of the tracks. As I do, I've also been idly flicking through the wikipedia bios of the musicians on the record, and came across this picture of Al on his (though very little additional info, even though he lived to 86).

 

Anyway, to the point of this post - what is all that ironmongery on his headstock? And would anyone have a clearer picture of something similar? Just curious!

 

Thanks in anticipation.

[itu]

https://doublebasshq.com/gear_posts/what-are-double-bass-extensions-and-how-do-they-work/