I almost bought one of these locally but then discovered that it was missing its glass window. I'd have to dig though my files to make sure that my memory wasn't playing tricks on me, but I could have sworn that I've also seen variants of this design that were made in different materials - not wood.

It's funny that these covers were marketed as being soundproof when you know that there would still be noise creeping out of the line space lever and keyboard openings. It would be fun to experiment with one and actually determine just how much it reduced the noise level of a machine, which in the case of this eBay auction was mistakenly described as an "Underwood 12" (I think it's an Underwood Model 6 with a 12 inch platen).

Speaking of the typewriter in that auction, it's important to note that it includes the correct modified model for use with such a cover. If you look at the carriage levers that protrude from the cover you can see that they are not standard levers, but ones that were lengthened so that they can be used with the cover closed. In contrast, look at the photo below that shows a regular Underwood standard inside the same cabinet (it's actually a narrower model). In that scenario you would have to open the cover every time to wanted to advance a line on the page. I'm sure that those who used these things found them very frustrating to work with, but imagine if you didn't have the correct typewriter for use with it.

Now that I'm thinking about it, would it be that difficult to make one - perhaps a smaller version to accommodate a portable?