I am not much of a typography expert. Unfortunately the word 'one' is very common so Google/Bing return no reasonable results.
Common examples include:
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I can assume 2 variants:
This is the version 1 of the font.
The PostScript type of the font is 1:
Type 1 (also known as PostScript, PostScript Type 1, PS1, T1 or Adobe Type 1) is the font format for single-byte digital fonts for use with Adobe Type Manager software and with PostScript printers. It can support font hinting. It was originally a proprietary specification, but Adobe released the specification to third-party font manufacturers provided that all Type 1 fonts adhere to it.