Now that you are able to remove the current lock, order a new key and lock cylinder keyed to the rest of the car. The new cylinder comes with one new key.

Given it's an old lock and the high probability of lock lock (heh) older Mercedes ignition locks have, it will be cheap insurance in the long run, and you're back to one key operation.

Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles