The pre-cast concrete block looked inconspicuous from the outside(other than the stamped date), but once it was removed we found metal lifting eyes and a mortared rectangle on top which looked to be hiding the vault. A few whacks with a sledgehammer (and some help from the excavator bucket) revealed the contents that have been under cover for the past 80 years. Unfortunately, there were no relics, no gold coins, just a soaked copy of The Pilot (the Catholic newspaper, presumably from the week the convent was opened).
Here’s to finding the next time capsule!