Canada Stamps - Keep Fit (1974): 632a (DF), 632ai (HB), 647a (DF-LF) & 647ai (HB)

A nice example collection of an extreme fluorescence difference! It contains four se-tenant blocks from the 1974 Keep Fit issue in their different fluorescence. The blue summer blocks were issued on a dull fluorescent paper (#632A), but also in a bit scarcer hibrite version. Therefore, the contrast between the DF and the HB copies is staggering! The red winter blocks were issued on a dull fluorescent to low fluorescent paper, but they were also issued on a much, much scarcer hibrite paper, almost ten times more valuable than the regular version! Therefore, this set contains:

• #632a: Summer block on DF paper
• #632ai: Summer block on HB paper
• #647a: Winter block on DF-LF paper
• #647ai: Winter block on HB paper