This is a paper lid opener for Showa-era milk bottles. There are four openers. The red, blue, and pink ones are for Meiji Milk. The yellow one says "Aluminum is Post Mark." The Meiji Milk openers are for Vita Meiji Milk, Gold Meiji Milk, and Meiji Honey Yogurt. The size is approximately 6.7 cm long (excluding the string). They have been stored at home, and I think I received them from the milkman and left them as they were, but it's unclear if they were used. The string on the yellow one is broken. There is also fading of the text, discoloration of the needle, and scratches. They cannot be sold separately. Thank you for your understanding.