Tombstones of a Sahaba and Tabayeen?

Translation
In the name of God, Most Gracious, Most Merciful
Oh God, when you gather
all the people (those of old and those of later time)
to the appointed day (Meeqat)
make Hafs bin Umar one of the companions of Mohammad
Peace be upon him
Amen
God of the two worlds


Anyone have any information on this companion?

Translation
In the name of God, 
Most Gracious, Most Merciful
Verily in
the messenger of Allah ye have a good
example for him who looketh
unto Allah and the Last Day 
and remembereth Allah much. Oh God 
keep Abdullah bin Mohammad
bin Abdullah bin Hassan
al-Hashmi among the youths 
of Heaven - Amen




I think this tombstone may belong to a direct descendant of Imam Hasan. Imam Hasan had a son, Hasan Muthana who had one son: Abdullah, who had four sons -> Muhammad, Ibrahim, Idris (who went west to North Africa), and Sulaiman (who went east to Persia). The individual mentioned above could possibly be the son of Muhammad. Also, this tombstone is from the Fifth century hijra; thus, adding more substance to this claim.



NOTE: The details about Hasan Muthana's sons come from a Shia website. They in some cases have conflicting information on the number of sons/daughters etc. But, this info sounds reliable, as Idris did go to the West and was a Hasani. Interesting point to note, the author of the text claims to be a descendant from Sulaiman (who went to Persia). In contrast, as far as I know, most Idrisi Syeds are Sunnis in North Africa. As a Sunni, I am inclined to think that Syeds in Persia may have converted to Shia school due to the reign of Safavids. 




Allah knows best.