Welcome to the world of the White's MXT! I would start with the concentric coil (950.) Get the feel of the machine with the way White's originally released it. The 6x9 Eclipse is a good DD coil to start with as well. Hit some playgrounds and learn the feel. This is a very powerful relics machine, but will do well for coin shooting. The important thing is to swing a bit slower as your new MXT has an incrediblely fast recovery time and you will find your headphones flooded with sound which you will find overwelming until you learn the concept of a repeatable response from a target. Once you can seperate out all the ground noise, EMI, and trash this synphony of sound will mean a lot more to you and you will be able to pick out the good targets more readily. Don't be in a hurry! You have yourself one of the most powerful single frequency machines on the market. The ground tracking ability is still one of the most advanced even after all these years. Most of all have fun, and enjoy. You will be finding some amazing things in your journey with this machine. When you pull that first Silver out of the ground... stop and think about why you just dug a keeper out of the ground that has held it captive for so many years. Good luck!
Keep Swing'in
Jack