Quite simple.....
I have two sets of IMSTO PBT sets. One is blue, one is grey.
They each have a couple keys missing. I dont remember which ones and I dont feel like unpacking them to find out.
If you combine keys from both sets you have a working set.
Meanwhile, if you decide to source the missing keys you need here on geekhack you have two working sets that sell for about $90 each new.
I am asking for $25 shipped (wow!) for both sets.
