Leg,
In theory all the A2's where rebuilt C7 uppers (not A1's) that whent in got a new flattop - and had the lower re-done. Most where then re-annodized (first batches) We had the first issued A2 series guns - which is where I got the pics and the colour generalization from -- I heard from others in Pet -- that it look like exactly what you descirbed and they got lazy and simply did a quick parts swap and never anythign more than that...