The new batch has a better counterbore where the pump handle bolts screw in. The machine shop made the hole and c'bore in one operation with a special tool last time, while the new batch was done with two operations. This gives a more square surface for the pump handle bolts to seat against. The o-ring groove was also widened 0.005" for a slightly looser o-ring fit. Both changes are minor and do not really warrant an upgrade from the last batch.