[stevenpetryk]

I'm quite certain the typeface is Computer Modern (the primary font being CMU Serif, to be precise). It can be found by Googling it. I also distribute the fonts as an NPM library, since they are OFL. [1]

[1]: https://github.com/stevenpetryk/computer-modern

[rzzzt]

Ah, so it has TeX/Metafont origins: https://en.wikipedia.org/wiki/Computer_Modern