What is the rarest Tomy/Plarail/TrackMaster item you own?

2nd generation ひかりごう. Some people say that his mold is even more rare than the first generation as it was manufactured in 1970 for only 2 years before transtioning to blue white ひかりごう. There are 2 types of this, one with window band and one without. I heard the one with window band is the transitional mold and it was manufactured for less than 5 months before turning blue white. Sorry, but not even in the consideration as one of the rarest.