My 1988 190E uses the one 424A (24"). It is not listed in the Bosch book either, but works great. If you look at the end tips of the A & B there is a difference. Not sure what is different except size of the tip.
The best thing to do is go to Autozone or Pep Boys, they will install them for free. Now I know it is not hard to install the blades, however they will be able to fit the correct blade and try the different ones without you having to go back in the store and returning multiple blades after opening the package.
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