Any time the Bank, which started at $20,000, was broken. The Bank went unclaimed for quite some time during the Master Puzzle era (due to couples either quitting, running out of Bank Cards, or finding the Bankrupt Card)...and was finally broken for $53,323.
The way the Bank Vault prop was revealed in each Stunt-era episode was pretty cool- the Vault prop would glide forward, the backdrop of the set would darken, and dramatic music would play. Very suspenseful. Say what you will about the rest of the show, but Kline & Friends had the visual look nailed.