Number group Earliest known date Front design Designator ------------------------------------------------------------------------------------ 50,000,001 December 2007 ? Handy Hints T-b1 to T-b4 to 50,100,000 50,100,001 January 2008 Handy Hints T-b1 to T-b4 to 50,200,000 50,200,001 December 2007 ? Handy Hints T-b1 to T-b4 to 50,300,000 50,300,001 January 2008 Handy Hints T-a1 to T-a4 to 50,400,000 50,400,001 December 2007 ? Handy Hints T-a1 to T-a4 to 50,500,000 50,500,001 June 2007 Handy Hints Bus T-a1 to T-a4 to 50,600,000 50,600,001 June 2007 Handy Hints Bus T-a1 to T-a4 to 50,700,000 50,700,001 July 2007 Handy Hints Bus T-b1 to T-b4 to 50,800,000 50,800,001 July 2007 Handy Hints Bus T-b1 to T-b4 to and T-c1 to T-c4 50,900,000 50,900,001 June 2007 Handy Hints Bus T-b1 to T-b4 to 51,000,000