Did you have it in AM? Pure platinum is LESS conductive than iron. Iridium is is less conductive than gold. It wouldn't surprise me that the 90% platinum ring with iridium might actually give you a 1, 0, or even a negative number and if you have disc'd out iron, maybe wouldn't get a peep. If you were in AM and still didn't hear it, then I dunno other than to say that besides conductivity, the detector can also look for ferrous and non-ferrous components in the signal. The problem is compounded by the fact that both Beach modes are set up with low frequency weighting which makes them more tuned to hitting high conductors like silver and copper. This is partially a tradeoff to enable the Beach modes to balance against salt conductivity which mimics gold. So the thing that gives the Equinox great stability in salt surf, also tends to make it hit less hard on gold jewelry vs. the "2" modes and Gold modes. Of course Park, Field, and Gold mode, especially, are basically unusable in salt surf or even wet salt sand. The beach modes can hit mid-conductors at depth (nickels and gold) but mainly that is because the signal to noise ratio is very high in Beach mode as the salt is cancelled out, so if the target has some conductivity, you can hear it. But as you get further down the conductivity scale with the likes of platinum, you are going to have a hard time picking it up. Regarding, the 95% Plat ring, not sure what the 5% metal alloy mixed in is, if it is a high conductor, then that will help it become more visible even though it has a higher concentration of platinum. Just educated speculation based on what I know about the material properties as an attempt to offer an explanation. There are many other variables (size and shape of the target, orientation to the coil, etc.) that can affect the results. Another factor, not sure if you were testing at the beach, but if you were air testing over regular soil that had some degree of mineralization, Beach 2 scales back transmit power in response to detected "black sand" mineralization conditions, so that can affect the signal strength. Again, just grasping because I don't have the complete picture on how you conducted the testing. Interesting results, thanks for sharing.
