If you are really after performance using a Magnetic induction system has significant draw backs for high performance and high rpm. There is a reason a Capacitive Discharge system is chosen. Or the coil over plugs. If you only have to fire a coil once every revolution, the time to saturate the inductor is much greater by 8x, so even at 12000 rpm you have 4x more time or 10msec to charge the coil. Plenty of time.

Taking apart a bad box to examine not a waste in my opinion. We take everything else apart and mess with it.

Left is an Mopar black box 4111850 from late 70's I assume. Other probably a Standard product box. The Mopar is better constructed, heat and noise shielded with the board. Double grounded to case. Automotive standard. The other barely had the transistor heat sunk via friction, poor construction, and components with age issues. (Electrolic caps). Single ground. Different design too, but that could be an improvement or necessary for the power transistor.
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The box sand should be a special silica for heat absorption and transfer along with protecting from environment. Whether the compound used meets a high standard???? Prestolite boxes I have seen never have the epoxy potting compound fail. The Mopar boxes do not age well. The compound on the SMP product wasn't full bound to the box. Most came out in hunks allowing the board to be removed easily. I guess you get what you pay for.