I wanted to follow up on this post. I ended up using Adler Windows to replace my windows. They obtained the proper paperwork from the Landmarks Commission. We had a few hiccups, but I would definitely recommend this company. To elaborate further, some of the windows were not a perfect fit and Adler Windows had them remade; I brought this to the attention of Adler Windows. There are a lot of vendors that would have stuck me with the windows because the measurements were slightly off and the moldings would have covered them. On the other hand, I hired a top rated company and they wanted to ensure that I was completely satisfied.
There are a few tips I would like to share:
1) make sure that you get a picture and model number of the window that is being installed
2) make sure that the window specifications are in the work order, e.g., vent locks, color of hardware, painted, primed, unpainted, etc.
3) have somebody take the measurements independently from the window vendor and compare the measurements
4) on installation day, take the time to cover your floors and if you can put padding around the area where the workers will be working - you want to avoid scratches and dings on the floors
5) after installation, check each window's hardware to make sure that they open and close easily and that the window can be disengaged/re-engaged for cleaning the outside panes while the workers are still present
6) if they are installing window handles, have them measure the exact place where they are drilling to ensure consistency throughout all the windows