(Sorry for the way too large photo, I have no idea how to make it smaller). I made a couple key heads using W123 grille emblems (key sandwiched between two of them). They were very difficult to make, involving many steps. However, the end result was satisfying.
First, I removed the studs from the back, and flattened both emblems. I had to grind the edge of the back side so the key would fit in a recess. I used a 1/2" holesaw to make a half circle cutout for a small split ring. I then used epoxy to hold everything together. I am sure there is an easier way to make these. I want to encourage anyone to make these, as I think they are the coolest key head for these cars.