I purchased these metal drawing tools from E-bay earlier this year. The purchase was made after reading a plea on The Lead Adventure Forum, see this link. I already had a larger metal square that I had purchased from Flying Tiger some time ago, but this set was too much of a bargain to miss out on. For details of where I bought them see this link.
I use the metal squares when scratch building in plastic card. The metal tools can be used to both mark and cut the plastic card without any danger of damaging the edges (unlike the plastic drawing sets). In addition you can use them as guides when gluing plastic card together as the solvent will not effect the metal. However my Flying Tiger square is now a little worse for wear as I tend to abuse it.