Make sure you read through this thread: www.elitefourum.com/t/identifying-shadowless-unlimited-base-set-boxes-packs/16993/1
Basically, the only base set boxes that you can almost assuredly confirm are shadowless have the following characteristics:
- Green wing charizard on side
- Single country code
- No WotC logo on wrapper*
- Confirmed shadowless pack art via peeking
- Confirmed long crimp packs via peeking
* Not 100% on this, as far as whether there is such a thing as a logo-ed box w/ confirmed shadowless art, long-crimp packs
The one exception to this would be if the seller had a case, had opened a box and confirmed the cards were shadowless. This is highly unlikely though, and you’d be taking the seller at his word.
Best bet would be to put all the information you’ve received from the seller here so that the shadowless experts on the forum can validate the info he’s giving you.
With all of the above taken into consideration, a box with all 4 or 5 of the listed characteristics has not been, as far as I’m aware, been sold publicly for a very long time.
The most recent sale for a Green Wing, single country code, confirmed shadowless art, but short crimp packs went for $13k at the end of January on PWCC. Of course, box prices have been exploding since then. There’s just not enough sales for good data on this.