Well I know many people rave about the 6x10 but I am not a fan it is ok for hot ground. but it can be too hot at times, if your GND readings are below 75 I'd be using a concentric, they ID junk better and you use/need less Disc to wipe out junk/Iron.
Silver will come In in anything from the high 60's low 70's upwards and larger Copper coins will come in up to the mid 80's and modern coins come in at anything from 14 to the high 80's and pre decimal .500/50% silver coins will come in at around 52 an up, Which is a Bugga because depending on which era of pull tab it is they can come in at anywhere from about 10 up to about 26+/-,
What you need to do is carry a small note book and write a list in the right order of what Aussie coins come in at on the ground in your garden/yard. and when you go out keep it with you so you can cross check the ID's and that will speed up your learning and after a short while those numbers will become locked in your head, I carry one even now, even though I can tell what things are before I dig them, So give that a go, Coin and jewellery hunting is totally different from Relic or prospecting, So you need to get a note pad, No one here ever recommends using one, heavens know why because it will really speed up you hunting and boost your finds rate and Lower your junk rate until you can work it out in your mind, If you gave your machine to a complete novice with that note book that would speed up their finds rate In just 2 or 3 weeks and wisdom by about 6 months and within 2 to 3 weeks they would be whooping you, And not only that you should write down your settings in the back of the book and the depth details and what the find was for future reference,
Your detecting is being hindered by having nothing to compare your signals with, IE you dig a pull tab and the meter says "14", and you dig another and it says "18" and again and your up to "26" and then you dig the tail from one and it say "8". Yet any two of those numbers could be the same type of pull tab but why are the numbers different ? "Simple" the Depth. The Angle they sit at in the Ground, Is there Iron close by or near too, Classic example of that was my Etrac without digging the target it could give me 7 or 8 and even up to 10 different sets of ID numbers on the one target and the MXT and the Deus or the V3i are no different, because the angle and ground conditions and near by targets Good or Bad can all have an effect on your ID numbers,
The Skill is working out what the target is before you dig, Does it give a double bleep one way and a single one at 90* to your first sweep well that is sure going to be a long piece of non ferrous junk like a stretched out piece of can slaw or wire or copper pipe etc, or Does it give you a nice sharp bleep one way and a low tone the other, you just know that that bugga is going to be Iron, These things you can remember but with the good targets you should write them down as I said above,
If you use a note book and learn to trust the machine you will speed up your finds rate, and if your GND numbers are below 75 then use the 9.5/950 coil or the 12".300 Coil because you will get down to the deeper stuff, With the 950 coil I have personally dig Pre Dec Pennies at over 13 inches and I have never dug a coin over 8 or 9 inches and 10" is all you will get with a good Tail wind with that 6x10,
Do the Maths on the Coil 6x10= 6+10= 16 Divided by 2 = 8. So 8 inches is the average depth that you are going to get from that 6x10 coil on Coin sized targets remembering that that is the best results that you can expect from a DD coil of that size, A concentric coil can easily see to about 1.5X it's size in to the Ground, My more realistic View is a safer 1.3X it's size in depth.
So at 9.5" X 1.33 = 12.635" in depth on a coin sized Targets and again I have already dug large pennies at 13"+/-, Now compare that to what the 6x10 is doing. Not to mention the target ID etc. The 6x10 is ok for prospecting and it has good target separation too "IF" you are sensible with the Gain.
Even the Factory 10"DD will go deep too, but like all DD's target ID/Iron can become a problem,
I hope this helps and if you get stuck come back here and we can thrash it out, trust me it is really not that big an issue and very easy to solve.
Good Luck.
John.