Looking at the pictures of the AAHE in the
DGJ, the vent rib exhibits the concave ramp to match a regular frame with the concave top of the standing breech, which I would attribute to a retrofit vent rib.
Some vent ribs with the flat-topped standing breech and the flat surface ramp which I would consider guns built from the ground up as vent rib guns --
227370 02.jpg
230737 04.jpg
232169 02.jpg
236958 12.jpg