Some do like the 550 meters and some like me don't like them that much and we do a 180 conversion on ours.
The 180 meters were started with the Sun Rays when Minelab only had a bar type meter as we wanted something more precise with the actual numbers for those slight tone changes our ears have a hard time telling the difference in. It is used more for us that coin hunt as we can tell the difference in like the beaver tails off the older pull tabs and a nickle. It can tell the difference in the zinc pennies and the copper one by only a couple of numbers even those the tones may sound the same.
Now the early 550 meters came out on the XS2 Pro and the XS2 didn't have them, only the Pro had them, but could be bought as a accessory. I found out that the numbers were not as stable and many times overlap to a bad target on a coin, the number would vary much more on a deeper target so we had a harder time telling if the target was good or bad compared to the 180 meters. Latter on we notice when the XS2a came out and the Elite came out with the 550 meter it had been changed to a more stable 550 meter, so there is really 2 versions of the 550 meter and the difference is 1 resistor I know of as the kits come with both of them and you have to see what the value of R2 I believe it is to know which one to replace.
I have tried most all of the meters for the Sovereigns and like the 180 meters with the Sun Ray DTI 2 (later model) and the DTI 3 the best as I liked the angle on which the meter sits as it is easy to see, but these were around $170 when made back in the late 90s and early 2000 and once in a while you will see a used one and some do want quite a bit for them. The one Ron makes is by far the best deal I have ever seen on a meter for the Sovereigns and it seems like he is always trying to improve on his design to make them better.
As you will notice most people that post will be posting using 180 numbers, so those with the 550 meters these numbers don't mean that much and feel myself that the 180 number meters are more universal numbers. This is why I bought the parts to do the conversion so those that want to make their 550 meters into 180 meters.
Rick