9303 Part 4, positions 29 to 42: "Any special characters, including spaces,
in the personal identification number ... shall be replaced by the filler
character (<). The number shall be followed by the filler character (<)
repeated up to position 42."
So the field holds two different kinds of filler. The trailing run is
padding, which was already stripped, but a filler inside the number stands
for a space or special character substituted on the way in, and those were
printed as they came - a US passport showed its personal number with a '<'
in the middle of it.
Strip the padding, then put a space back for what remains. It is the
closest recovery available: the original could have been a hyphen, and the
MRZ does not keep which.
optional_data itself stays a faithful copy of the field. Nothing else
reads it, and it is the personal number that is being rendered here.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
