I finally got the Skyriter back from the repair shop yesterday. I have not looked up the serial number yet, but if I had to guess, I would say it is from the early 1950s. It is extremely easy to type on, and feels rock-solid. The extra features are pretty scant, but that is understandable, given the compact form-factor; the Skyriter is no larger than my Hermes Rocket, but typing on this one feels like I am using something more like a regular desktop machine.
I am really pleased with this typewriter, especially considering it was an eBay purchase and was pretty cheap.