Number group Earliest known date Front design Designator ------------------------------------------------------------------------------------ 51,000,001 July 2007 Bus - Handy Hints T-c1 to T-c4 and to T-d1 to T-d4 (Jan 2008) 51,100,000 51,100,001 Not seen as yet to 51,200,000 51,200,001 July 2007 Bus - Handy Hints T-a4 (4 x slogans) to 51,300,000 51,300,001 July 2007 Bus - Handy Hints T-d4 (4 x slogans) to 51,400,000 51,400,001 August 2007 Bus - Handy Hints T-a4 (4 x slogans) to 51,500,000 51,500,001 November 2007 Bus - Handy Hints T-d4 (4 x slogans) to 51,600,000 51,600,001 November 2007 Bus - Handy Hints T-a1 to T-a4 to 51,700,000 51,700,001 Not seen as yt to 51,800,000 51,800,001 October 2007 Bus - Handy Hints T-a1 to T-a4 to and T-b1 to T-b4 51,900,000 51,900,001 January 2008 Bus - Handy Hints T-b1 to T-b4 to 52,000,000