Well! How nice to be wrong when thinking this might have to go to the mystery category. It’s normally quite painstaking to identify (if we get lucky) unknown buildings. But this one was found in Google images of domed churches showing right up at the top. No scrolling, even! The building in the foreground is the original church, but see a full description of both buildings in this Wiki article.

And, of course, this is a Real Photo Postcard, and according to Playle.com, this style of Defender stamp box logo dates from about 1920 – 1945.

Divided back, Real Photo Postcard, unused. Defender stamp box. Circa 1920 – 1945.

Price:  $20.00

Sources:  First Church of Christ, Scientist. n.d. http://en.wikipedia.org/wiki/The_First_Church_of_Christ,_Scientist. (accessed May 24, 2015).

Real Photo Postcard Stamp Boxes. Playle.com. Web accessed May 24, 2015. [http://www.playle.com/realphoto/photod.php]