Amazingly the company still exists. They're now known as Inscape and are still in the business of selling office furniture. So if you want some office furniture you know will last they may be your guys.
I contacted their information mailbox with a few questions, and received a very nice and quick response:
Good Morning Kevin:
Thank you for your wonderful email regarding your Office Specialty desk. Office Specialty has been in business since 1888. Imagine, 124 years now. We manufactured wood products up to 1954. We then started manufacturing all steel products. All of our wood desks were made of quarter-cut oak, walnut or mahogany. 110 was built approx 1920. Do be so careful in restoring and keeping these numbers for value and antique reasons. So your unit is around 100 years old. I receive emails from all over the world and it is so exciting to know where they all end up. I would appreciate knowing where you are from Kevin. Would also very much appreciate a picture of your desk for my files.
110 is the serial number of my desk. Turns out the desk is about thirty years older than I'd thought!