The font in use appears to be the ‘9×14’ bitmap font (i.e. 8×14 glyph bitmaps tweaked for 9×14 character cells) of the Hercules graphics card. The title of the video is ‘Windows1 (1985) PC XT Hercules’; I guess that’s something of a dead giveaway. This font happens to be substantially (if not perfectly) identical to that of the original IBM MDA card.
In the ‘VGA Text Mode Fonts’ collection, glyphs from
FONTS/PC-OTHER/HYUNMGR9.F14 and a few others appear to be consistent with what is seen in the recording. Those font files are not identical, so there must be some glyphs that differ by at least a few pixels, but I have not noticed a perceptible difference in the characters seen in the video.
Other than slashed zero, particularly characteristic are the shapes of the glyphs for ‘6’, ‘A’, ‘M’, ‘V’, ‘W’, ‘Y’, ‘b’, ‘f’ and ‘y’, especially the latter three: the notch in the ‘b’ glyph, the longer horizontal stroke of the ‘f’ and the shorter tail of the ‘y’ distinguish the MDA font from the EGA font.0 Below is my attempt at reconstructing the screenshot with one of those fonts:
If you open the above image in a viewer that can interpret ‘pHYs’ PNG chunks, you should be able to view it in the original 4:3 aspect ratio. Though if for whatever reason you cannot find one, here it is again with aspect correction.
The website you linked in the comments offers this font as IBM MDA, but without aspect correction. I presume this might have thrown you off, leaving you unable to recognise it.
0 The EGA font is also shifted one pixel to the left within the 9×14 character cell compared to MDA, but this is much harder to notice, if even possible. Those three glyphs pairs are the only ones to differ in shape.