"Choker."

I have a couple of them. They've been around a long time, maybe centuries. Flamenco guitarists use them a lot, not to change keys, but, essentially, to shorten the guitar neck and bring the frets closer together for fast fingering of runs ("falsettas") and such.

When I got my Arcangel Fernandez flamenco guitar in 1961, I found one of them in the string box in the case the guitar came in. Standard equipment. I prefer them for nylon-string guitars.

The Spanish word for them is çejilla, pronounced "say-HEE-yah."

I often use a Shubb (got two of them), but I prefer the çejilla.

Don Firth

P. S. Memorabilia. Hmm. Gotta think about that.