Can anyone give me any information about packs of "Happy Occasion" notes put out by Conoco? I bought a box of them at an auction, and there are no dates anywhere. There are probably 200 or more envelopes with "Conoco" imprinted on the outside. On the inside is a birthday note, a Thank You note, a Congratulations note, and a blank note. Any information as to age, value, etc., would be appreciated. Thanks! Tom