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?"
"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?