That boss is to keep band mounted shifters from sliding down the downtube. They were common before braze on shift levers.
Exactly 👍.
Nice! I have an old frame with brazed on diamonds to stop the DT shifters slipping and the FD dropping down, very subtle.
@johnnettles2 started
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That boss is to keep band mounted shifters from sliding down the downtube. They were common before braze on shift levers.