Can someone help me identify this mark

[zhirarosado]

[waywardangler]

I am afraid the mark has disappeared into thin online air.

[mariok54]

maybe it's sideways on? 

[waywardangler]

Would there not be a thin line then? ______ Or would that have been construed as the mark? It could actually look the same straight on or sideways on then but straight on could also be a . Time will tell what the mark is or isn't but mark my words, I don't think it is a . or a ______ 

[KC]

It would make a marked difference to be able to see the mark! 

[hosman321]

The X with a white background usually represents target practice. 

[waywardangler]

KC, you are on the mark and hosman has hit the target!

[mariok54]

Could be a quote from the Sting!