If you don't wanna get into looking at valvecovers, and such, here is a better list to look for.
If it's an Si, it will have rear disc brakes (90-91)
If has a moonroof it's an Si.
If the wheels are factory, and are alloy, it's an Si.
If the redline is 5500 it's an HF
Si, and HF have badges, DX doesnt.
Anything else is a DX
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My cars:
Civic coupe EJ1. B16A, EG6 cluster. Wrecked/parting.
CRX DX ED8. DOHC ZC, I/H/E.
EJ1
Civic Si . Screw Hatchbacks. Coupes just look better. Period...