papas52,

From what I could gather here Group 5.188 - Cover is the Master parts Catalog listing for these. See snapshots below for more details. Your metal ones were definitely original equipment.

A web search for GM# 475516 provided links for sales listings (none mine) in eBay for NOS or OER items and reproductions available from Chevs of the 40's (https://www.chevsofthe40s.com/detail/6298/Chevrolet_Brake_Adjuster_Hole_Plugs_Original_Metal.html)

Your call if you want to use the rubber ones you already have or if you want something period correct???

Hope this answers your questions.

Dan
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~ Dan
1951 Chevy 3 window 3100
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