Frustration But Still Fun Day

I thought I would be clever and use a real estate assessor website to find the old properties around my city. The only problem is every site that I found from 1900-1910 when I got there was either full of the usual "No trespassing, police monitored" or was private property ( not surprising), and I can't imagine them willingly letting me and my little brother start digging all over their property. Also there were no parks in this certain strip of old properties just an old church which was in session. Anyways we went back to his elementary school since he said his teacher lost a silver bracelet because some kids thought "They could turn it into buried treasure" which they apparently did. No such luck with the bracelet, but got $1.50. Sorry for the long story, but what would be an effective way to find some silver coins. By the way, all state parks are off limits with a 1st class misdemeanor punishment. Any help would be appreciated!