I usually go with:
Subject: Name heading, [name]
Subject: Name heading, [name], [title]
[Depending on whether I'm writing to the publisher (or someone else, not the person in question) or the person in question]
I am a cataloger at Quality Books Inc., and we are distributing [title] to libraries. In order to complete the cataloging, I would like to get more information about [the author/whatever the person did/you]. According to library cataloging rules, each person responsible for the overall content of a work needs a unique name heading, in order to distinguish the works of one person from those of another person of the same name. May I please have [person's/your] middle initial/full middle name and/or year of birth so that I may create a unique name heading for [person/you]? Also do[es] [person/you] have any previously published works?
[Sometimes including a list of possible other publications].
Thank you for your assistance,
Quality Books, Inc.
The Best of America's Independent Presses
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I hope this helps,