Couple of things to consider here:
First most gold coin or ring-sized targets, regardless of purity, are going to ring up in the high single digits perhaps all the way up to 20 or so, depending on total mass of metal. The majority of coins and gold rings will ring up between 10 and 17. Gold alloy rings up as a mid-conductor just like aluminum, lead, brass, and nickels and is hard to distinguish from modern trash as a result as mid-conductive targets will ring up in the mid-teens. I will usually ring up just like can slaw or a pull tab. Nature's cruel little practical joke on detectorists.
Next, regarding TID, specifically. You mentioned -9's. I take it you were detecting without discrimination, perhaps in "horseshoe" mode with no discrimination (also inaccurately referred to as "all metal" mode - Equinox does not have a true all metal mode (where the target signal is fed directly to the detectorist without filtering or signal processing). Anyway, to get to the point, if you are seeing a lot of -9/-8/-7 numbers and iron grunts going off, that is a dead giveaway that you have not properly ground balanced the machine because those are ground feedback signals. So make sure you ground balance as part of your normal startup routine. Also, one quirky thing about Equinox is that ground balance and EMI noise cancel as well as most settings are mode specific. If you ground balance in Park 1 you will also need to ground balance separately in Park 2 because each multifrequency mode will see the ground differently.
Finally, it appears you need to better familiarize yourself with the various modes and what types of targets they are optimized for. Briefly, Park 1 is set up for general hunting but is skewed towards high conductive coin targets by the nature of its lower frequency weighted multifrequency spectrum and 5 tone ID default. Park 2 is skewed towards small targets and mid-conductive gold jewelry as it is weighted to a higher frequency profile and is 50 tones. The field modes are geared more towards relic hunting. Similar to Park 1, Field 1 is skewed towards high conductors (lower frequency weighting) but is a simple two-tone (ferrous/non-ferrous) setup. Field 2 is geared towards lead, brass, and gold mid-conductive relics and is 50 tones (like Park 2). The beach modes are set up to run stable on a Salt Beach environment and though they are low-frequency weighted, can hit high-conductive and mid-conductive coins as well as gold jewelry at moderate depths. The Gold modes are high frequency weighted and set up optimally for gold prospecting but can also be used for mid-conductive relic hunting. The pitch-based VCO like tone does not provide tone ID but target ID is provided on the display.
So if you want to that gold coin to hit hardest, ground balance your machine in whatever mode you are going to use and lean towards Park 2, Field 2, or Gold modes if you want to focus on gold coins.
HTH. HH. GL.
