JMHO, the shell manufactures kept using the roll crimp method because that's what they had machinery to do. I would think the fold crimp was less costly to do - no OS card - so they eventually went to it. Maybe they glued the thin paper piece over the fold crimp at first because someone thought the customers wanted to see shells the way they use to be ? And they thought it made the shell waterproof. Just some ideas running through my head.
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Paul Harm
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