the top of the X-Terra series. Some manufacturers mess things up by creating too many models in a particular series, with the only difference from the lowest to the next being a simple feature or two such as adding Coin Depth, or maybe static Pinpoint mode, etc.
All three X-Terra's provide the basics of Pinpoint, selectable '0' (zero) discrimination (All Metal accept) or full-range notch rejection, Numeric TID, Coin Depth Reading, etc. They provide enhanced adjustments and/or features as you move from the X-T 30 to the X-T 50 and then X-T 70 such as more notch segments for a more refined setting (12 to 18 to 2

, expanded/enhanced Sensitivity adjustments and other basic adjustment features. More "Pattern" or "custom" modes ... with memory, (1 to 2 to 3), the addition of Manual GB, then the option of Manual, Auto, or Tracking GB, manual or Auto Noise Cancel with the X-T-70 and many many more.
I seriously think that Minelab, like any manufacturer, might make some running revisions here or there is they feel it necessary, but I doubt that there will be an X-Terra 100.
Monte