I did a little research and I think they may have been made at the Ionia Mfg. plant before it burned and was replaced with the plant next door that built the rest of the Mark IIs. Coachbuilt.com says that the company was acquired in '53 by M-B, but that doesn't jibe with the production dates.

I'm beginning to remember more about the letter. It spoke of being very concerned that the smaller firm wouldn't be able to keep up with production as they had already lagged in delivery. I seem to distinctly remember that there was a complaint about a car that had one door an inch longer than the other.

I'm wondering if M-B made the prototypes with Continental's dies and then got them back. Possibly they shopped for a builder and got a better price than M-B and let the initial production contract to them, but pulled it when they didn't perform and transferred the dies back to M-B.

I just recently read that there was a die material change that saved them $600 a car. This may have been the turning point.