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The OEM binder was produced by ALGI.
This company still exists but has not manufactured cycle fittings for many years.
One mail-order source for ALGI binders (also employed on stems) is Mel Pinto Imports.
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You may discover that the threads and nut size on the Gripfast binder are Whitworth dimension.
The firm was a supplier for Raleigh binders and wedgebolts.
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