The rear end of the barrel assembly has a metal cap

Using PH00 Screwdriver remove the 4 screws

Screws: 4@ M1.4 x 3mm wafer head

Use a flat blade screwdriver to carefully lift the cap at multiple points around the circumference. It is a tight fit.

Be careful when removing it, as there is a plastic spacer underneath.

There appears to be places for two spacers, but only one was fitted in this lens.