and duplication (these are often listed on the back of the check). Technicians at the National Security Agency developed anti-tamper holograph and prism labels that are difficult to duplicate. Product packaging Tamper-evident design is perhaps most visible in the process of product packaging and labeling, where it can be vital to know that the product has not been altered since it left the manufacturer. Cans of baby food were among the first high-profile cases, where manufacturers were extorted by persons claiming to have added various poisons to baby food and replaced them on supermarket shelves. The amount of stock which needed to be destroyed (because it was impossible to tell if a given item had been tampered with), and the threat of public fear, meant that tamper-evident design principles had the potential to save a lot of money in the future. Jars of food items soon started appearing with a lid with a metal bubble in the center, commonly known as a "safety button", pulled down by vacuum in the top of the container, which—like the lid of a Mason jar—popped out if the jar had ever been opened and stayed flat if the jar was in pristine condition. These lids would also pop out if the jar was contaminated by potentially dangerous gas-producing bacteria. Customers were advised to never buy a product with a popped lid. In addition to the visible flat "button", an intact lid makes an audible "pop" when opened. Newer jars of food tend to come with a plastic wrap around the edge of the lid, which is removed when opening, although the springy-cap designs are still in common use. Tamper-evident packaging also extends to protect stores; there are some scale labels for meats and deli products that will tear if removed. The 1982 Chicago Tylenol murders involved over-the-counter medications. Due to FDA regulations, many manufacturers of food and medicine (as well as other products) now use induction sealing and other special means to help provide evidence of tampering. Break-away components which cannot be reattached are useful. Custom seals, security tapes, labels, RFID tags, etc. are sometimes added. The current epidemic of opioid abuse and drug abuse has led to a search for tamper-evident strategies to protect central vascular lines. Drug users who shoot drugs into their veins often acquire infections of the heart valves (endocarditis), liver, bones, lungs, and other organs. Treatment of these infections