In many ways, the Dursleys are the first antagonists Harry ever faces in Dursleys do not care to look after Harry. The Christmas gifts they send Harry are further evidence of their disregard for their nephew, but they bear an intriguing relation to the Deathly Hallows.
The Deathly Hallows are three magical objects, and when wielded together by one person, it is said that they can become a master of death. According to the Wizard fairytale, three brothers evade death by building a bridge over a treacherous river in order to . Death appears, pretending to be impressed by their skill, and as an apparent 'reward' promises to give them anything they want. One brother wishes for a stone to bring back the dead, the second wishes for an impressive dueling wand, and the last wishes for something that will help him hide from Death, with Death reluctantly giving him a cloak that renders him invisible.
According to the theory (via top-grossing Harry Potter franchise and can be represented by the Dursley's (horrid) Christmas gifts to Harry. For his first year at Hogwarts, Harry is gifted a 50 pence coin by his relatives, which resembles the resurrection stone. Another year, he is gifted a toothpick, symbolic of the elder wand, and he is lastly given a single tissue bearing a resemblance to the invisibility cloak.
Not only are these gifts awful in true Dursley style, serving as another way for his aunt and uncle to remind Harry that he isn't wanted by them, they coincidentally carry a strong resemblance to a key plot point throughout the franchise. Given that the prophecy in Harry Potter was a highly guarded secret only known by a few in the series, it is doubtful that the Dursleys sent Harry secret clues about what the Hallows are. It is more probable that Dumbledore guilt-tripped the Dursleys every year into sending Harry a Christmas gift. Or, perhaps, a determined owl pecked at the Dursley's window so often each December that they eventually gave in, literally giving the owl the first thing they could reach; a 50 pence from a pocket, a toothpick on a table, or tissue from their sleeve.
It may not be a likely theory in of Dursley's being aware of the prophecy and the Hallows. Still, it is interesting, given the overall detail in the franchise, and could have made for another Harry Potter character's redemption in the final film. More probably, the gifts were a careless thought on the part of the Dursleys, giving Harry an even more tragic backstory. Still, Pottermania stirs up again amidst the Harry Potter cast reunion coming in 2022, garnering more attention to fun theories and small details in the franchise.