The S3 here is Rooted and running a custom ROM based off Samsung Jelly Bean stock firmware, can flash other ROM at buyers request.
Worth mentioning that this is a US variant S3, it is SIM unlocked and will work best on the Telecom network.
Other things to note about the US S3 variant is that it uses the Snapdragon S4 dual core SoC, rather than the Exynos one in the International version. In practice that doesn't really make a great deal of difference to the user-facing experience, although it isn't quite as adept at very intense 3D graphics (also its native video playback isn't as good for demanding files, however the MX Player HW+ decoder basically brings it up to par, and for some files even pulls it ahead of the International S3). GPS performance is slightly increased over the International S3 also, but if you're only using it for navigation purposes this won't make a great deal of difference to your experience (people into sports-tracking via GPS will likely appreciate the improved accuracy and lock strength however).
Being that it was purchased via Ebay it is safe to assume that there is effectively no warranty on this handset.
Some glamour shots of this S3 can be found here, and here.
It is in pristine condition so far as I can tell on close inspection.
Looking for around $500, will ship anywhere in NZ at no cost.