Reply to David Barrett,
Yes, the stone does "clearly" say that he died in Kislev. In the English text, it says just as "clearly" that he died on the 5th of December, which would put the date in Tevet.
I was merely pointing out this discrepancy.
The original poster has now pointed out that the secular date was the one in error, so Kislev it is.
Have a Gmar Chatimah Tovah.
Brooklyn, New York, USA