I have sent Tony some images of a MK2 Airsporter trigger block in its dis assembled form. It may help to establish what is required to repair or replace.
It is a smart design; as Mick mentioned it allows the trigger block to be indexed for correct alignment with the cocking slot.
A very handy function when changing out trigger blocks.
A PM has been sent to you Tony.
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Wanted: rear sight for Milbro Diana MK4, the slide elevation type. Or images to replicate from.