It's not the bulb wattage causing problems, but rather the discoloration and dirt on the reflectors and prisms. You need to clean the prisms, and paint the reflectors white. Add new bulbs, and you ought to be able to see the numbers at night.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.