The best set !
With apologies to those who prefer the white bordered , more common T206 cards...you've started the Mini-Monster!
There are a lot of T205 fans on this board, a very knowledgeable bunch who will surely assist in any of your questions.
I've completed the base set (quite a few years ago) and have been picking away at upgrades, Cycle backs, variations or even just more quantity to eventually start a second set. I have got a lot of them graded here :
http://www.sgccard.com/usersetcompos...usersetid=3598
Your Soveriegn back is one of the subsets that one particular pal collects (Hi Geno

)
The set, similar to T206 could be collected many different ways. I just love the set with its bio/stat back, ornate designs on the AL cards, more standard portraits on the NL cards and the super cool ML cards.
My advice...read all you can read about them and decide your direction.
It's not a very tough set to get 90% of the way, but the last 10% can be expensive depending on your condition requirements.
Welcome to the Gold Side!