https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-xap1/t1.0-9/10459913_666301253443943_6821582859753385393_n.jpg
https://scontent-a-fra.xx.fbcdn.net/hphotos-xfp1/t1.0-9/10402534_666301146777287_1929051984853562194_n.jpg
Does anyone know what this could be?
Looks like it could be a very well worn gold plated Chinese KK.
Yuki
Definitely a worn-down gold bearing. Very likely of Asian origin
thank you
I don’t know if it’s worn, but it sure spins like no other bearing I’ve ever tried
Well if it’s gold plated, as far as I know, the plating wears off pretty easily so that could just be string wear. Also most gold bearings you’ll find will indeed spin quite well.
YOYO BEARING, SR188 GOLDEN , Size: id 6.35* OD 12.7 * W 4.762mm would be my guess. 
Yeah, it’s not the first time I’ve had a gold bearing, but it’s the first time I’ve got one that worn.