A friend of mine had an old book press in his shop that he bought from an estate sale years ago.  When he found out I was looking for a shop press, it landed in my office.  I finally had a chance to try it out last weekend.  I used an 8" (diameter) Molon Labe sign made from 1/8" steel plate I had in the garage for the pressing.  As a first test, I cut out an insert that fits into the dash of my 2006 F250.  I was a little skeptical that I could get enough pressure with the book press to make a permanent mark, but it actually pressed relatively well.  I left it in the press for just over an hour before letting it dry and dying the embossed region black.  I've already ordered a pair of 1/4" plates cut to fit in the press for a better surface as well as some additional embossing plates (buddy owns a steel shop).