I was pretty sure that the pristine looking woofers in the Mission 710s I got last week weren't original, but wanted to confirm it. I was right. The original Peerless woofers were long gone. After some deliberation, I installed a set of Seas woofers that would've been in 770 Freedom 4s. The new woofers polypropylene cone and more rigid cast chassis, combined with the same Seas tweeter used in the first 3 generations of 770s, make them sound much more like 770s than Missions original bottom of the range speaker.
Thanks to The Speaker Shop team for sorting out a crossover issue for me.