Shape has absolutely nothing to perform with coil form, it's all in how They may be internally wound. There is also no "most effective" coil. You no doubt Have a very concentric coil as that is certainly exactly what the Goldmaster II arrived with. White's called it a Longscan" simply https://irs-approvedgold00900.blogoxo.com/38017153/the-fact-about-silver-and-gold-investments-that-no-one-is-suggesting