I wonder if it is for the SE rather than a 128k/512k(e)/plus. I have heard of upgrades for the SE included SCSI thanks to some weirdness in the onboard SCSI hardware (slow or something).

The 030 sounds like an appropriate upgrade for an SE and the May '93 date on the CPU makes it a good bet.

Edit: SE Motherboard may not fit due to the PDS slot unless it is meant to cover the slot.

Going by the Plus logic board, it looks like the RAM would get in the way with all 4 slots full.