I have this fairly nice stamp and am hoping to get some confirmation here that it is in fact a C grill or ???? I know there are limitations to imaging and that this is a big ask, but I trust that some useful direction may be obtained here on this forum.
Here is an image of the entire stamp and TIA
Further complicating the analysis is the fact that the stamp is on cover and for that reason I am unable to show the back side of the stamp. I tried to get a side view but did not achieve a good result. My thinking is that the ink from the pen cancel show a vertical ridge which I think is an indication that the grill is up from the back as opposed to down on the stamp. On top of all of that it is a fairly faint grill and that complicates it identification. At least for my old eyes.