Jim,
Some of us just take a quick look at some of the post and have time to respond right away, some dont, some like to give it some though before saying anything and then there is some that just like to keep informed on what is happening and some of the question and answers there is.
Anyway the Sovereign has to me a better tone ID as you know you went over a target and sometimes I feel it even sees more targets than the Explorer as the tone is nulling or changing more than the Explorer does, or what I can hear. The Sovereign if it is 4 years old will have the tone ID like all of the Sovereign, that is unless someone has opened it up and tinkered with it. If it is a XS2a they had a switch too to make it a single tone on the face of the control panel too, so make sure it is set to multi tone. It is important before you buy to see if the control box was opened up and tinkered with. I think if you can get one with a 180 meter mod you will like it better than the 550 numbers for IDing and also for learning the detector and its tones.
Rick