Max lifts the larger phone revealing the smaller one underneath.

Miniature telephone concealed in what looks like a standard telephone in Maxwell Smart's apartment.

This unit is in the same location as the previously seen Pot Plant Phone and Telephone Gun.

Max speaks on the mini-phone.

All three may in fact be the same device.

[Episode #30: "The Last One in is a Rotten Spy. Compare with the Mini-Phone used by Agent 99 in Episode #59: "A Man Called Smart, Part 2".]