"I'm glad you find it so." I tell him, quite honestly. The fact that he finds it useful means he uses it regularly, which provides me with more data by which to shape the parameters for future projects in the same vein.

He removes it, and I pointedly turn away, so as not to see where it is he hides it when he's not wearing it.

"No." I say, equally artless. "I am not going to tell him."