The original Tandy Coco I did not have lowercase letters, but instead had reversed color version of the uppercase characters to represent lowercase letters. Later models introduced true lowercase fonts in the Coco model 2B.
This is an example of the original fonts with the first characters in reversed colour.
To test your Tandy Coco (or emulator) to determine if it has true lowercase fonts you can enter this small BASIC program.
1 POKE&H167,&H39:POKE&HFF22,21 10 FOR I=0 TO 255:POKE 1024+I,I:NEXT I
Note these pokes may prevent the tape drive from saving until the system is reset on some systems
Here is the output with true lowercase letters.