Originally posted on Tinhte, the video claims that the Galaxy S3 has a 4.6in AMOLED high definition screen with a resolution of 1,280 x 720 and a pixel density of 320ppi, making it almost identical to the 4.65in Galaxy Nexus.
There's also an eight megapixel camera with LED flash, 2050 mAh battery and NFC support to make contactless payments - all in all, very similar to the Nexus, which we reviewed in December.
As you would expect, the Galaxy S3 is running Android 4.0 (Ice Cream Sandwich) and inside there is a 1.4Ghz quad-core processor with 1GB of RAM and 16GB of internal storage - there's also a MicroSD card slot to bump that up even more.
The phone does not appear to have a physical home button although the video does claim that, because the phone is a test unit, the final production model might look different, but the screen and specifications will be the same when the phone is announced on 3 May.
Earlier this week we reported that the Galaxy S3 sports the model number GT-i9300, and this video states the same, further adding to the reliability of both reports.
The video goes far beyond any leaked images we have seen of the Galaxy S3 in recent months, with the user shown operating the phone close up, with clear shots of the phone and its operating system.
Samsung said on Thursday that all images claiming to be of the S3 so far have been "not even close" to the truth. We've asked Samsung for a response in relation to the video's credibility but at the time of publishing, we have not had a reply.
Engadget approached Samsung for a comment, but all the company had to say was: "We will be able to tell you more at the 2012 Samsung Mobile Unpacked."
IBTimes UK will be attending the Samsung media event in London on 3 May, where the company will almost certainly announce the Galaxy S3 - although so far all we know for sure is we've been invited to "Come and see the next Galaxy."