On education.ti.com one day, the 8XU OS upgrade for the TI-84 Plus/Silver Edition changed to OS 0.46 temporarily, likely as a mistake. Before it was removed, this file was retrieved from the server and placed into the community's hands.
It appears to be an early release of OS 2.21, which was the first 84+/SE OS. Its internal layout is very different, and contains much more test code than 2.21, particularly with USB communication. While sniffing around, I discovered several pages of code to be sent to a USB printer.
Below is what I've discovered and proof that TI was tinkering with oncalc USB printing on the 84+/SE.
I extracted the PCL commands from the OS and ran it through print8x to see what it contained, and here are scans of what it printed:
Your guess is as good as mine with this, but I'm going to say that they ("they" meaning Hank and Steve) were testing USB communication and thought "hey, why don't we throw some PCL at the bulk IN pipe of a USB printer and see what happens", and so they did. And apparently they're Mavericks fans.
Steve Falaster, if you're out there, I'd be really curious to know what this is all about.
Everyone else...if you don't believe me, "find" OS 0.46 (I can't give it to you) and look at 77:7634h.