One contained a collage of paper scraps. The other, a small saucer with two messages: "Congratulations to Michael Tolson for everything you've achieved so far" on the front, "Well done, Michael + Lenka" on the back.
That night, he learned his neighbor had gotten odd mail. Soon, he found other neighbors received weird letters, too.
It turns out, nearly every residence in the city's Polish Hill neighborhood received letters - 620 in all - as part of a project by artists Michael Crowe and Lenka Clayton.
Crowe and Clayton, both 32, say they want to write to everyone in the world. In April, the pair wrote 467 letters to homes and businesses in Cushendall, a small Irish village. The Polish Hill letters were their second undertaking.
They picked Polish Hill because they both happened to be in Pittsburgh and felt the size of the neighborhood suited their needs. Pictures of the letters can be seen on their Web site, mysteriousletters.blogspot.com.
Crowe lives in London. Clayton is from England, but moved to Pittsburgh in September with her husband after getting a "vision where I saw the word Pittsburgh written in yellow block fancy letters," she said in an e-mail interview.
The artists said they hoped the letters might prompt curiosity and chatter among residents.
Last week, the Polish Hill Civic Association was flooded with people asking about the letters, said Leslie Clague, an association staffer.
Polish Hill was settled by Polish immigrants who came to work in the city's steel mills in the late 1800s. The massive Immaculate Heart of Mary, where a Mass is still said in Polish on Sundays, dominates the hilly neighborhood about two miles northeast of downtown.
The neighborhood is still about half Polish and many of its residents are elderly, but is now also home to many artists.
Clague works in several media, including sculpture and drawing. Tolson is a conceptual artist who goes by the name "tENTATIVELY, a cONVENIENCE," or Tent for short. He had suspected from the start that his two pieces were mail art, in which people send artistic creations through the mail.
But some recipients were put off.
One elderly woman was terrified because her letter implied the writers would pay her a visit. Another resident received a letter saying how nice she and her husband were. But the man had died and that made the woman uncomfortable, Clague said.
"They have a really fantastic idea, and it's really beautiful, but I think they could have spared a little bit more of a thought about how it might come across," Clague said.
Tolson thought the project showed the artists' incredible vision. He plans to hang the saucer on his wall. He also appreciated that it got people in the neighborhood to talk more.
"We're well aware not everyone will love the letters, but we're also happy with the idea that neighbours chat about how awful the letters are, and so get together over a lovely old moan," Clayton and Crowe wrote.
Anna Misiaszek, who runs Alfred's Deli Plus with her husband, said the letter that arrived at their shop seemed silly. It read: "Next time someone tries to bamboozle you with the cup and ball trick (on holiday in Turkey, at a city bus station ...) choose the cup on the right."
"This is something crazy. I treat this like a joke," she said Tuesday.
She initially tore up the letter and tossed it in the trash, but later retrieved it when she was told it was an art project.
Isaac Bower, a sculptor, called it, "Artsy-goofy. I thought they were pretentiously trying to be mysterious." His letter referred to an obscure book, but suggested he probably wouldn't take the time to find it and read it.
Crowe and Clayton spent about 10 hours a day over two weeks writing the letters, 70 each day.
"It's an absolute pleasure and absolutely difficult too," they said. "Anything positive and friendly that pops into our heads is generally considered suitable. ... The more cryptic letters often come at the end of a 10-hour writing session. Or the very start." They acknowledge the mixed reaction.
"One charming man (who didn't receive a letter) has suggested the IRA should bomb us," they wrote. "Others have spoken about how magical it was to walk around town asking everyone if they also got letters, and how because of the project, they are now on first name terms with several neighbours."
On The Net:
Mysterious Letters: http://mysteriousletters.blogspot.com
Polish Hill Civic Association: http://blogski.phcapgh.org