The spring is 1m long, close coiled, Ø6.0mm OD Ø1.0mm wire and made from C51000 Phosphor Bronze, 5% Grade "A" Spring Temper H08.
It is joined with a 'spring' made from the same material that is 30mm long and Ø4.27mm OD (to be a tight fit when 'screwed' into the Ø6.0mm spring).
The assembled band...