Platinum client
In theory, only the most important, strategic clients of the firm are platinum clients: That five percent that accounts for ninety percent of the firm's revenue.
But, on the lips of any salesperson, however, it means “my client" the particular client — or client prospect — in contemplation at that very instant, however tawdry, pissant or strategically irrelevant. Particularly when it has just said "all of our other counterparties have given this".