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One thing to keep in mind regarding Bob Jackson, JRJ and Merlin (steel) badged framesets it that only some were produced in house.
Many were done by cottage industry builders in the surrounding area and delivered to the Jackson facility in bare metal for painting and transfers.
It is entirely possible that one of these contracted frames might be nicer than an in house produced one.
Do not know if there are any details which might decode the difference.
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