This is a fantastically blatant copy of the Shimano 600 EX 6200 of 1978. The ‘555’ designation has a curious echo of Shimano’s ‘333’ logo. SunRace have even copied the Shimano’s weird psychedelic Arabesque patterns that are so reminiscent of Jimi Hendrix’s legendary visit to Morocco - perhaps the whole derailleur looks better when you are comprehensively stoned.
Unfortunately there is a hint of nastiness about the finishing. Otherwise this would be the first perfectly kitsch derailleur.