here i have a mystery vintage bike exhaust tightening collar that is made from some form of alloy
ie - brass \ bronze etc.etc.
as can be easily sen from the 3 images - 2 of the small fins have been drilled
this will have been done for securing with wire,
possibly when racing
many road bikes had this modification carried out !
some of the fins are slightly bent over,
this will have been caused by hitting them to tighten them up..
at the top end of the threads
there is a saw cut mark,
as this damage is at the top
it may not cause any problems..
the internal diameter is 42.5mm.
if you know as to what this exhaust ring fits
please let me know !!