That is a great find! Especially being younger that would be really exciting. Hopefully the property owners identified what they could of it and it is on display somewhere on the grounds. It would be cool if even there was something on the display tag that read “Found by 4th grader on ground while on tour on date etc…”.
I haven’t myself found anything that exciting. Another member made a post about some things they found near an old fort in Bayonne, New Jersey. Hearing stories like these inspire me to dig a little more into the historical Philadelphia maps and see what areas might be legal and open with permission to responsibly uncover a little history.