Originally Posted by The Saint
The "you're fracked" letter would tell you in no uncertain terms that they've determined the item unacceptable and will destroy it after the appeal period expires, or something along those lines. Since your letter says it's being held for the purpose of determining the item's admissibility, you really should call in and explain politely and accurately why it's not for a real gun.
I agree with Saint, and if you can somehow do some intense research on the differences and in detail point out something like no serial # or something that it's not for a real gun and it's for a toy than you can get away. But on a lower frame heh good luck.