Ah ok it is a 512k upgrade, probably why the ram chips are socketed. Impossible to find the data sheets on the ram chips unfortunately. Quoting you @Unknown_K from this thread in VCEF in 2018:
Just pulled out my other 128k and yeah the original looks different.

I pulled the card out of my Tandy and it is a PBJ Inc MFB 1000 c 1985 with 2 rows of Mt1257-20 chips. Those are 256Kx1 so I have a 512KB upgrade (16 chips)?
Just pulled out my other 128k and yeah the original looks different.




