The .70 Euro stamp in the 2009 tourism series featuring pipe organs is the organ of St. Martin's Church, Dudelange. The "Grand Orgue" was completed in 2001 by the Thomas Jann firm and has four manual divisions and pedal. It incorporates pipework from the church's earlier instrument by Stahlhuth, but reverses some mis-guided work on the 1960's and now encompasses 72 ranks of pipes. The impressive instrument, not surprisingly, is the focus of an international organ music festival each year. One may view the stoplist and image here.
I recently found this page which give some information about the organ (it's a CD sales site), and this page which describes concerts and other activities related to the instrument. I also found this image of the exterior of the church. The church appears by happenstance on a Luxembourg stamp issued in 1955 celebrating the completion of, of all things, a television antenna in the region. I'll load an image of that stamp soon.