German site mobilegeeks.de has an image of the upcoming device, which Samsung says it will show off very shortly, alongside a crop of specifications.
Most interesting among the rumours is word that Android 4.1 Jelly Bean will come pre-loaded, and the smaller 4-inch display will sport a 800x480-pixel resolution. That's a lower resolution than the Galaxy S3's 720p display, but fewer pixels count equate to a much cheaper mobile.
The processor is supposedly a 1GHz dual-core model -- which is significantly less powerful than the 1.4GHz quad-core chip that's lurking inside the phone's bigger brother.
A 5-megapixel camera is reckoned to be adorning the phone's back, while a 1,500mAh battery and 16GB of storage are other rumoured specs. If you want more storage this mobile is expected to feature a microSD card slot, which should make it simple to bump up the capacity.
The design is exactly as you'd expect: a slightly smaller version of the Samsung Galaxy S3, with the same rounded, pearlescent finish. Based on the hardware though, this phone isn't going to be a shrunken version of the hugely-powerful Galaxy S3 -- these specs paint a picture of a distinctly mid-range mobile that has only its name in common with the Galaxy S3.
Take everything you see here with a pinch of salt until Samsung's big reveal tomorrow -- we won't know for sure what this phone looks like or what it'll feature until the South Korean tech giant lifts the lid itself.
Samsung already makes mid-range Android phones -- the components listed here are similar to those of the 4-inch Galaxy S Advance, for instance. Perhaps Samsung is taking advantage of its flagship phone's recognisable branding to try and flog some cheaper, mid-range mobiles.
What do you think? Are the specs listed above an anticlimax, or are you still excited to see what Samsung has to show off? Tell me in the comments or on our Facebook wall.
Image credit: mobilegeeks.de