Yes, they were bolt-in. If you open/remove the inner part of the taillight (the one that holds the bulbs) you will see 6 nuts (8mm head) that need to be unscrewed after which the inner reflector can be taken off and the outer lens can be taken out.

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)