I travel quite a bit, but I haven't figured this out yet.

Every couple of trips, I will pick up my suitcase from the baggage claim when flying, and find that it has s decent amount of yellow chalk smeared on it. Not completely covering a single side, but still more than just a tiny bit.

These are all domestic flights within the US, and I mainly fly Delta. My luggage has just "normal" stuff in it (clothes and toiletries)...

Does anyone know what it is from, or why it is there?

Farewell - June 4, 2020