Adam is correct that all of the box lock guns built by todays AYA, today, use the same action.

That said the XXV-BL, as created and produced by the original AyA, was based on the model Iberia. This is a XXV-BL from 1968:





Here is a catalog entry for the Iberia:



Thats the genesis of the XXV-BL.

The post DIARM AyA is a much smaller and much simpler operation than the original AyA. They are unable to offer the different actions that were available from the original AyA and that why were now seeing the same action on all the box locks.
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