Are the books, papers, watch, and glasses belonging to my grandfather, which were found in the possession of my deceased father, and which my uncles did not claim during his lifetime, considered the share of the grandfather's heirs or my father's heirs?

If your uncles were unaware of your grandfather's belongings being with your father, then this is an infringement on his part, and you must return these items to the heirs for division according to Islamic law, calculating your father's share. However, if they were aware and waived their right to them in favor of your father, then they have no right to claim them now. If they did not waive their right, then they have the right to claim them now. If the matter is uncertain, the original ruling is that these items remain the property of the heirs, and their ownership does not transfer to your father except with legal proof, while giving your father the benefit of the doubt. It is important to know that the division of inheritances is a limit set by Allah that must not be transgressed, as Allah Almighty says: "Those are the limits [set by] Allah, and whoever obeys Allah and His Messenger will be admitted by Him to gardens [in Paradise] under which rivers flow, abiding eternally therein; and that is the great attainment." (Quran 4:13) And as the Prophet, peace be upon him, said: "Indeed, Allah has given every possessor of a right his right," and "Whoever leaves behind wealth, it is for his heirs."