That mysterious font actually is an adaptation of one of the oldest typefaces around specifically designed for optical character recognition. OCR-B (1968), by Adrian Frutiger. It’s used everywhere still, on credit cards, wire transfer forms, license plates, etc. etc. It’s even an industry standard (ISO 1073-2:1976).

https://en.wikipedia.org/wiki/OCR-B

So, it’s as ‘custom’ as Apple’s (pre San Francisco) systemfont Myriad, compared to Frutiger’s Frutiger, who said of the adaptation: “not badly done” while feeling that the similarities had gone “a little too far”… — https://en.wikipedia.org/wiki/Myriad_(typeface)