You are correct in noting that the equipment rules clearly state that the length must be marked on the ski.
However, it appears that the ski does meet specs, assuming that the radius marking is accurate.
So, the decision goes over to the start referee. He might say that you can't start because the length is not marked as required, or he might be satisfied that your skis are long enough (maybe by comparing to another ski that is marked). The start referee is not obliged to take any extra steps to confirm if your equipment meets specifications, but there are many who would do this on your behalf.
If you were allowed to start, someone who might have noticed that your skis were not marked might launch a protest, and then it's up to the jury to decide if your run stands.
Your coach might approach the start referee or a jury member before the race to sort this out ahead of time, rather than just hope for the best at the start gate.
How strictly the rules are enforced is probably going to be influenced by where the event is held, who is competing, and what is at stake in this race.