This is a U-lock from SAIKO. It locks the wheels of motorcycles and bicycles to prevent theft. It's harder to cut than a chain, so I think it offers good security (though it's not 100% theft-proof). It only has one key. I don't use it much anymore because it's a bit cumbersome to carry around, and I think I bought it over 10 years ago. There are scratches on the protective cover from when I dropped it. See the 5th image. I've confirmed that it works. Please refer to the images for the condition and length.