curious, anybody run into this?

Not an A-body issue. I bought a used 02 ram 2500 w/5.9L Magnum engine, 118k miles. The engine oil dipstick has a "twist" built into the last 5/8in of the dipstick, and on this last 1/2in of the stick, there is this "coating". It is very thin, looks kinda "charcoal" black in color and texture. I can't tell for sure if it's a manufactured feature, or what its purpose might be. For all I know, it could be hardened sediment coating. Anybody seen anything like this before? It's kinda driving me crazy.