Boler door window

[rosey45385]

Thanks to those who replied about converters and inverters ? Answered. I have another ? All pictures I have seen most bolers have a small narrow door window that opens. My 72 boler 13 the door window is 21 x 21 and does not open I have only seen pictures of 5 other bolers with this larger door window. I would like to change window and gasket but not untl I find out more info about it