Ah, just had a look. Yes, that is 'Heinrich Siedel'. True 'Yellow
King Humbert' is one of the 'spotty' Cannas and is very variable
sometimes producing petals that are half yellow and half red, or
flowers that are all red or all yellow. Add to that its tendency to
produce purple variegated leaves as well as leaves that are wholly
purple and you have a highly schizophrenic plant. It also goes by the
name of Cleopatra.

Since there is a variety similar to Florence Vaughan called Cleopatre
amongst the Crozy group of hybrids, it doesn't require a huge leap of
imagination to understand how Florence is also confused with Yellow
King Humbert! Cannas are in a heck of a mess and so far no-one
appears to have the courage to sort them all out. It doesn't help
with every man and his dog raising seedlings from named varieties and
pushing them out with the parental name either.