It looks like it has 1 MB soldered on and that can be doubled by adding a 1 MB expansion ram card.

The official part number for the expansion card is PC-PA7139U. But good like finding any info on it. Internet searches are pretty sparse.

My later Toshiba T4900 uses a slightly more standard memory card that Kingston makes. The only thing I can find that MIGHT be what you're looking for is this here - https://www.ebay.com/itm/113471794930

Tha ks for the response.
Mine has a board attached via ribbon cables. It has some chips mounted and some empty placements for more chips. I wondered if any one had identified what chips would go in these places?
I'll put up some better photos in a few days, this is a stock image from the web.

Another internet image showing the basic 1mb chips. Half the number of positions for the 2nd 1mb of ram

Recently i wondered the same thing and ordered some TOSHIBA DIP-20 TC514256AP-10 chips. I am still waiting on them.

Here is my logic - I am no expert and dont really know what im doing so please correct me if im wrong.

Although i have never seen one the PC-PA7139U 1MB LIM-EMS 3.2 memory card sounds like it may be a separate card going in the Toshiba expansion slot so i assumed you cant get 2MB on the ribbon cable card.

The ram chips on the card with the ribbon cable and 4 unpopulated spots do seem to be wired in a similar fashion so i assumed same type just through hole packaged.

Because the RAM has a separate battery backup i got same brand and speed DRAM - power use was low on 100ns type
Im using 4x 1/3 AA size, 1.2V 250mAh NiMH batterys in series - should it be NiCD? is this bad? Sorry off topic.

Marketing at Toshiba may have decided sales on the 1MB add on card would have been affected by a 0.5MB upgrade selling 4 DRAM chips and keeping expansion slot free.

If all the support circuity is there and BIOS is cool with it we may get 1.5MB total. Would be nice to have a RAM Disk that's about the same size as the floppy drive.

The only other thing i can think of is its for parity RAM. I have seen this on a 8088 that already had 640kb ram and empty ram sockets, a jumper set parity on/off - I dont think this is what its for. The chips for parity would be smaller capacity.

Hopefully someone who has done this before comes along before my RAM chips do!

Good luck with the refurb, worth the hassle of getting it mobile if only for the weird looks you get using a vintage computer in public places.

Oooo, I'm glad I'm not the only one keen on this.
I'm fascinated to see how you get on. My plan is to trace out the connections for the thru hole components and then get four 512x4bit chips and try it.
Good luck and please do let me nnow how it goes.