Check the listing for details. MEI 4 in 1 credit card bill validator reader head. Condition: Used. Listed at 75.00 USD. The MEI 4 in 1 credit card bill validator reader head is a versatile device designed for businesses and industrial applications. It is capable of reading and validating various types of credit cards and bills, making it a convenient and efficient tool for managing transactions and payments. With its advanced technology and compact design, this reader head offers a seamless and secure solution for processing multiple forms of payment in a single device.