Accidentally admitting owning something

Watching Top Gear the other night, and whilst on their caravan-train someone whips out a sound pressure level meter.

"Oh look..." I say, "... that's the same pressure meter as ours."

"The same what?"

"Pressure meter"

"How long have we had one of them?"

"Ah, did I not tell you? Oh, it's been ages now..."

What other items have you inadvertently admitted to owning?