I'd consider 4:28.7 to be a good 500 time.
FFS, I'd hope so! That's less than 1sec/100y off the pace of Katie Ledecky's best 500 ever, and damn near good enough to qualify for men's NCAA D1 championships.
In the context of this forum (adult triathletes, many without a competitive swim background), I 'd say sub 6:00 for men under 55 years old, and sub 6:45 for women under 55.
That would put you somewhere around a (unofficial) USMS "A-time" for most age groups 25-54. An A-time would be 120% of the average of the last 3 years 10th best time in the age group for that event.
[EDIT] After looking at the USMS motivational time charts again, I realized I was looking at the AA column for women. Changed my bogey time from 6:30 to 6:35[/EDIT]
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