Experienced stamps need a home too. I'd rather have an example that is imperfect than no example. I collect for enjoyment, not investment. APS Member #223433 Postmark Collectors Club Member #6333 Meter Stamp Society Member #1409
A stamp with a grill should have a rectangular series of "puncture wounds" in the stamp which you may be able to see or even feel. Tilt the stamp, use a magnifying glass, all the usual things. The slightly darker or "stained" area on the first stamp appears to be a grill, but only you can be sure.