This K & E Keuffel & Esser Co. 4053-3 Polyphase Slide Rule comes with a black leather case and is a must-have for collectors and enthusiasts of engineering and science history. Made in the United States, this slide rule is a high-quality piece that is perfect for display or use. With its sleek design and durable construction, this slide rule is a great addition to any collection. Its polyphase feature allows for precise and accurate measurements, making it a valuable tool for engineers and scientists alike. Whether you're a collector or a professional in the industry, this K & E Keuffel & Esser Co. 4053-3 Polyphase Slide Rule is a great investment.