Possible Clues:

• Bond first bought by FDR in 1941
• WWII bond designation
• US government bond category
• W.W. II bond type
• F.D.R. purchased the first one of these bonds
• War-bond designation
• Category of savings bond
• '40s war bonds
• Bond type whose first purchaser was F.D.R.
• W.W. II bond designation