The printout is dated 10-SEP-75 and is labeled "VERSION 3.0 -- MORE FEATURES TO GO".

Curiously this isn't the oldest extant version of the source code. The Harvard archives have a copy of version 1.1, printed on 30 April 75. http://altairbasic.org/other%20versions/ian.htm

The printout also contains dates 6-SEP-64 below it, any idea what those are?

Thank you for the warning. I once used up my Internet package's entire monthly quota by following a similar link on Hacker News.

Ironic for something designed to take up only 4KB on its target machine :)

(It's a high-res image of the printed code.)

Nice one. Has anyone OCRed this back into text?

I attempted OCR with OCRmyPDF / Tesseract. It's not great, but it's under 1% the size, at least. https://github.com/pronoiac/altair-basic-source-code

Maybe you should try something like EasyOCR instead: https://github.com/JaidedAI/EasyOCR

Feel free to run EasyOCR against it and submit a PR