It's the original resting place of the Rebbe, Reb Yochanan of Lutsk/Karlin-Stolin, youngest son of the Rebbe, Reb Yisroel of Stolin, זצ"ל. This is the Stoliner Celkah in the Washington Cemetery in South Brunswick, NJ. A.K.A. Deans. Reb Yochonon was buried there "al tnei" after his passing in 5716, and a year or so later was moved to Tverya, Israel. There are lots of stories about that - maybe for another time.
חדב"נ ר' עזרא שוחט, father of the Karlin-Stoliner Rebbe. Interesting choice of words on the מצבה. I assume the Stoliner Rebbe authored it. The מצבה is off to the side, in deference, I suppose.
I chose this matzeivoh mostly because of the reference to the "חסידה מאדמו"רי קרלין-סטאלין" which is engraved here. You wouldn't see that on the matzeivoh of a Hungarian Jewish woman...
