So i just discovered that Nissan calls this the "ECM" (engine control module). It is part number 23710. The full part number is usually(?) listed after the NISSAN, where on this ECM that is blank

it is substantally different than the 1200 ECU which is part number 22604 (engine control unit) and which only controls the carburetor a/f ratio via 18-pin connector

This ECM module has what looks like a 116-pin connector. Im thinking it is a modern fuel/spark computer

here's the modules on eBay, looks like the same numbers except the last 4-digit number

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  5ZE15M with programmed key.jpg (189.19 KB)