Brompton BSR chain guard disc
Brompton chain guide disc for Brompton BSR, SA-3, SA-5 and S5/2 hubs
Can be identified as the centre hole is smooth (the BWR / 2 speed equivalent has notches to match the 9 splines on the driver used on those wheels)
This video from Brompton shows how to remove and replace the sprockets.
Brompton Q part code: QCHGD-SA
Brompton part number: 9024100
Sturmey Archer code:
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