The Duet body is to be made of die-cast zinc with a silver colored plating. A very common planting material is nickel, but unfortunately it is also a meterial that many have an allergic reaction to. Our goal is to use the most body safe materials possbible, so in that spirit we are avoiding nickel. The above test (coin that has nickel vs our parts) is checking this on some preliminary Duet body parts. No pink on the cotton swab = no trace nickel = Good!