Early prototype boards used the Toshiba part and this is the part number on the schematic. The production boards all use a Sandisk part SD9DS28K-8G which is on the BOM. The two parts are JEDEC compliant and interchangeable.
I do have both datasheets, unfortunately I received them under NDA, so I can’t forward them to you. You will need to ask Toshiba or Sandisk (or their distributers) directly to get the datasheets for the Multi Chip Package (MCP) parts.
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