I have a 1537G US Stove Hotblast furnace and thought it would be great to have a glass door. Well I did it:
I decided to put the window on the Lower Half of the door since it would give me the best exposure with the inner Smoke flap. We machined 3/4 Slots above the window and Also in the slider. You can shut off the airflow or slide it to the left to adjust the airflow. I am hoping since it will draw air down across the glass it would work as an airwash to keep the glass clean.
This only took a couple long nights to do but I can't thank my machinist/Fabricator/landlord (Tom Bulduc in CT) enough. I always get him roped in these projects but even he thought it was a heck of an improvement.