RAM : 1568 / 1568 steps with Radio-Shack TRS-80 for PC-4 module.  This is not a PB-100 as it has at least the S+EXE combination and STR$ function,  Tested OK on april, 4th, 2024
Box
The 1k extension memory  Box of the extension 1ko - CAT. No 2636-53A