The rear axles on these old machines have thick polyamide (formerly leather) straps fixed to the chassis and wrapped around the axle case. These are to prevent over extensions of the shock absorbers at maximum  articulation of the axles…. (an unlikely event)

Check strap ready for sizing
Cut to size
Holes measured up and drilled on the pillar drill (10mm dia)
A bit hard to see but the 4 fixing holes in the chassis can be seen on the angled  plates. A good dose of copper slip is applied to the threads.
Check straps in place and ready to be bolted up