Here are 2 promotional items for "Project Sonic" on the Saturn. They are something that was most likely released together, probably at an event like a convention or trade show. The left item is an ink-pad type stamp. It stamps the logo, and the 'hand out' Sonic silouhette that's printed on the sides of the cube. The white thing at the bottom is likely to be its ink-pad and cover. This one, in the photo is likely to be especially uncommon because it is still unused, mint in the package.
The left item is a set of stickers for the project. You get 2 of each size, one black & the other reversed. There's also the Sega Saturn logo there as a sticker at the bottom. It's a pretty big sheet of them too, as you can tell by the tape measure there.
But what was Project Sonic?
It was an attempt to promote Sonic games even more, but with a focus on Japan-only. The Genesis games weren't as popular there as they wanted them to be (but they were super popular everywhere else) so they made up the Project Sonic to really ramp him up on the Saturn with awareness.
However, everyone knows the Saturn was kind of ill-fated and didn't have a mega-hit Sonic game on it like other systems had. That means this project was too. These items were likely from the start of the promotion at Tokyo Game Show 1997 which was also the year of Sonic Jam. (But remember, Jam was pretty much a re-compilation of previous games, and some 'goodies' like art and music as unlockable extras, it wasn't really a game in and of itself) The only other 2 games it got were Sonic R (Which was fine) and 3D Flickie's Island which was less than fine once all opinions came in.
Then, the whole thing got snuffed out by the Dreamcast and Sonic Adventure 1 which was the best game by far (out of those 4 games because 3D had slow Sonic, Jam wasn't a game, and R was fine but when you compared its graphics with SA1 (at the time--remember these 'opinions' are a product of the age of release) it didn't stand up and also it was a racer-only while SA1 was unprecedented in its plot thus-far in the series
So that's why you don't really hear about the project much, especially outside of Japan.