By Bobby Tanzilo Senior Editor/Writer Published Sep 24, 2013 at 10:10 AM

The world is full of minor mysteries and this weekend I stumbled upon an extremely minor one while leading an in-depth Doors Open Milwaukee tour of Maryland Avenue Montessori School.

Up in the attic, I found a circular symbol drawn in chalk on one of the walls. In the center of the circle is a bat with the letter "A" and the date "1991" beneath it. Around the outside above the circle is the word, "Dustbusters" and on the bottom, two names: "Dave R." and "John W."

I'd likely seen this before and paid it no mind. But this time it caught my eye because when I was up in the attic at Eighth Street School a couple weeks ago, I saw nearly the same symbol drawn in chalk.

The same circle, with two shaded sections flanking the bat. The same 1991 date. Dust Busters, now two words, at the top and "John" and "Dave" listed a bit off center, to the left, with no last name initial and no "A" beneath the bat.

I tried a little Google search and all that came up was a listing for a cleaning company in Milwaukee called "Dust Busters." While this seems like a possible connection, would a cleaning company actually deface property with graffiti (even if, really, no one seems to mind much, and in neither case were these so-called Dust Busters the first to chalk something up in these attics)?

Yesterday, I posted the pictures on Facebook hoping to learn a bit more but that, so far, has led nowhere. Do you know these Dust Busters? Have you seen this symbol elsewhere in town?

Inquiring minds want to know.

Bobby Tanzilo Senior Editor/Writer

Born in Brooklyn, N.Y., where he lived until he was 17, Bobby received his BA-Mass Communications from UWM in 1989 and has lived in Walker's Point, Bay View, Enderis Park, South Milwaukee and on the East Side.

He has published three non-fiction books in Italy – including one about an event in Milwaukee history, which was published in the U.S. in autumn 2010. Four more books, all about Milwaukee, have been published by The History Press.

With his most recent band, The Yell Leaders, Bobby released four LPs and had a songs featured in episodes of TV's "Party of Five" and "Dawson's Creek," and films in Japan, South America and the U.S. The Yell Leaders were named the best unsigned band in their region by VH-1 as part of its Rock Across America 1998 Tour. Most recently, the band contributed tracks to a UK vinyl/CD tribute to the Redskins and collaborated on a track with Italian novelist Enrico Remmert.

He's produced three installments of the "OMCD" series of local music compilations for OnMilwaukee.com and in 2007 produced a CD of Italian music and poetry.

In 2005, he was awarded the City of Asti's (Italy) Journalism Prize for his work focusing on that area. He has also won awards from the Milwaukee Press Club.

He has be heard on 88Nine Radio Milwaukee talking about his "Urban Spelunking" series of stories, in that station's most popular podcast.