I have a 1936 Ford Cabriolet that has a "fixed" non opening mail slot window in the rear fabric panel. The car was completed in about 2008. I've only had the car for under a year and the prior owner was unable to furnish various details about the build. The mail slot window exterior frame dimensions are 6.75" tall and 24.75" wide. The inner and outer frame is held together with 6 screws across the top and bottom and 2 screws on both sides. I think it might be a LeBaron Bonney window ***embly. I've been considering having this window replaced with a Sid Chavers "Cool Slot" window, the type that opens up to 90 degrees. I would like to get feed back from other rag top owners that have this "Cool Slot" window design; the pro and cons.
From what I can see on Sid's website, the closest window size to yours is 7" X 24", so may take some modification to your top to make work. For $1100 bucks I'd sure grow to love what you have. Mick