More than a decade ago I had an embossing die made and I have used that on all Cibachrome prints. I also emboss B&W proofs and finals like this, specifying a deep white or black border (for fibre paper or Cibachrome, respectively). Why? Because I could never agree as to how I should sign my name, so an emboss settled the argument for all time — for me at least!! :rolleyes:
I never sign anything on mats, framed or unframed. Just the hidden emboss for perpetuity and let the image speak for itself.