1♦: At least 3 ♦ cards in the East's hand. 4 starry players at this BBO table. West fully understood 4♦ and reached the best contract. East has 4♥ and a minimum opening (2♥). 3♦ on 2♠ would show good ♦, thus 4♦ should mean something else.
Benefits include:
Plus... it's free!