Long and Kees, the architects, embedded their names here and there, the architectural equivalent of Hitchcock appear in the first reel of his films.
I'm guessing the fellows might have been Masons, or known some.
If you head up the block, you'll see another addition, stuck on in the 80s, and see the big old front door which isn't the front door anymore.
Warning: do not expect to see any lumber exchanged. It's been a while.