Tandy Color Computers 1 and 2 can be configured with either Color BASIC, or Extended Color BASIC. These are two 8K rom chips in their own sockets on the motherboard. Many Color Computers shipped with only Color BASIC, and an empty ROM socket for upgrading to Extended Color BASIC (ECB).
The 24-pin ROM chips with ECB on them are no longer easy to come by, and 24-pin EPROMS are not common either.
I made these adapter modules to make it easy to upgrade machines using common 28-pin EPROMS. They’re designed to use either a 2764 or 27128 type chip (only the lower 8K of a ‘128 is used). These fit American CoCo2’s and “F” board CoCo1’s perfectly, and will even fit a “D” board CoCo1 (barely).