This is a brand new part, not old stock. Original dealer part, not a fabrication. This magnetic plug has a deeper socket than the original, and also comes with thread sealer.
#18 on the diagram, and later model cars use this for the fill plug, as well (#20, instead of #19 & 21).
Also fits Chevrolet Sprint, Pontiac Firefly & Sunrunner.
Note— the differential fill plug can be found here— eBay 324938868231
See my other listings for more hard to find Suzuki & Geo parts. Combined shipping available.