Your memory is excellent, Art. 1990 240 ignition switch is p/n 9447805. Fitment is listed as 1990-on 240, 1985-on 740/760/780 (includes prior to airbags) and 1991-on 940

If it isn't the ignition switch (would also be my prime suspect with such odd symptoms) and all fuses are double checked as okay then my next guess would be possible multiple problems, including a bad CPS as one of the common suspects for a mystery no-start with no spark.

The LH 2.4 OBD system can be used to quickly and easily verify there's a CPS signal getting through to the ECU. Refer to Engine OBD diagnostic test mode 2 (DTM 2) on port 6 in the 700/900 FAQ here, except it fails to note don't turn the ignition off after attempting cranking in order to keep the OBD system alive during and after the test as that also will turn off the flashing LED. As much as there are Check Engine OBD codes for a missing CPS/RPM signal (1-3-1 on port 2 and 2-1-4 on port 6), in my experience they are rarely ever set unless it's an intermittent/weak signal. (The ECU knows when it's getting the signal, but doesn't know when the signal is completely missing as it seemingly can't tell the diff between that and the engine simply not turning over, so a bit of a Catch 22.)
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now