Sovereign 350s with the apple green backs are much tougher than their forest green Sov350 counterparts, but what makes this Chance Yellow portrait a little tougher is the fact it is 1 of the 6 superprints in the T206 set. I believe, however, that it is not as difficult as finding a super print with Sov 460 reverse.
Some great reads:
http://t206resource.com/Print%20Group%205.html
http://www.net54baseball.com/showthread.php?t=144282
Thread specifically speaking on the difference between Sov 350/Sov 460 for the 6 super prints:
http://www.net54baseball.com/showthread.php?t=124890