Baseball Card Binder

When Dad removed the China Trip photo album from the shelf, he exposed what appeared to be a Monopoly property deed. Upon further exploration it was discovered to be a baseball card that had fallen out of an adjacent binder full of baseball cards. Dad flipped through the binder, but the only card we got a good look at was the one that had fallen out.

The card was Fleer card #123 from 1990 featuring Kansas City Royals outfielder Willie Wilson, wearing jersey #6.

Below are images of the front and back of the card from other sources.

Theories
By adding up the 3B (triple) numbers for the players in the "Marcia" and "Greg" locations on the Brady Bunch grid (top two corners) on each page, a possible combination of 9-4-7-8 is obtained.

Entering the combination into the realtor lock worked - a key has been obtained. It is not yet known where this key should be used.