Petroglyph

Oftentimes when I’m shooting pictures of old trains or rusted machinery or digging through oily machine shops, I find unusual marks or symbols on some of the components. While some of the symbols are signs to precaution mechanics or obvious makers marks, some prove to be inscrutable seemingly more ancient petroglyph than anything else. Here’s one such mark:

It really burns my toast though that I didn’t notice the rain on my lens while snapping this shot; hindsight, eh?