I said they were in rough shape, and they were (still are, in some places). The main thing for me was rebuilding the baffle that had been cut away to allow the Advent tweeter, with it's square magnet, to be installed. Then I could install a pair of original equipment Seas, and check out some Missions I've never heard before. They're very good. If memory serves, they sound better than 737s, and closer to 770s (with which they share a tweeter) than I would've expected.
It's interesting that Mission's designs using this particular Seas tweeter place the tweeter above the woofer (770, 717), while others of the same line and vintage (70, 700,707, actually most 700 numbered models) that use different (often Vifa) tweeters, place the woofer on top.