Joined: Jun 2010
Posts: 2,136
Likes: 1,524
From: Medford MA
Bikes: Ron Cooper touring, 1959 Jack Taylor 650b ladyback touring tandem, Vitus 979, Joe Bell painted Claud Butler Dalesman, Colin Laing curved tube tandem, heavily-Dilberted 1982 Trek 6xx, René Herse tandem
Could also be adhesive from old and long-gone rim tape, if no rim tape is present currently.
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Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.