Filles de Calvaire and Symbology

Alright, here's a bit of random-sighting ephemera from the Techno Parade:Here's rue des Filles de Calvaire, where Carla and I rented an apartment for a lovely week last summer. Remember this view, Carla? This is looking down "our" street from the métro station during the Techno Parade. Nostalgiarrific!

Also, I found this neat bas-relief over a portal on a building called Les Arquebusiers. Anybody have an idea of what this might mean? Erika: aside from general trinitarian connotations, do you recognize this symbol? Just curious. The old Templar site is in this area, so it wouldn't surprise me at all if there's something going on here.