It is a relevant possibility if a coin is known to be missing, but the sound alone cannot confirm its location or exclude another fault.
Understanding this situation
Check pockets before loading and inspect only safely accessible areas after the machine stops and cools as required. Do not probe gaps or push tools through drum perforations.
A useful next step
If the rattle is new or persistent, stop further use and report the missing object and programme stage. Do not keep tumbling the load to make the coin emerge. An engineer can assess retrieval without improvised internal access.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.