79pmooney The lugs on the Claud Butler aren't typical lugs at all, but a bilaminate faux design with welded tubes beneath reinforced by these. They were proprietary for Claud Butler and only used on the Olympic Sprint and Avant Coureur models in the early to mid-'50s. Quite rare.
I mentioned the Nervex Professional, which are the "typical" ones you refer to, because I brought those up in the initial post. Unrelated to the Claud Butler frame!
-Gregory