Door Hinge Bolts to Body Use Gaskets/Sealer ('65 ABody)?

What did the factory use with the 12 bolts (that have attached metal washers) that are used from the body to the door hinges? I can't tell if that was so kind of fabric/rubber washer or some kind of silicone/sealer? Those seals, whatever they are, disintegrate during disassembly.

Regardless, what are forum members using when putting things back together? Thank you.

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