Model 200 RAM
The model 200 comes with 24k built in, and supports up to 2 more banks of 24k in the form of ceramic dip modules that plug into the Option RAM #1 & #2 sockets.
TANDY 26-3866
The original 24K module was Catalog Number 26-3866.
This is a ceramic DIP carrier with 3 8k sram chips and a 40H138 to decode A13 & A14 into 3 different /CS for the individual SRAM chips.
DIY Modern Replacments
https://github.com/bkw777/TANDY_200_RAM
More info
https://archive.org/details/Model_200_Portable_Computer_Service_Manual_19xx_Tandy/page/n75/mode/2up