Just curious if anyone can explain this postage rate:

It appeared on a #10 envelope in a recent bulk mailing I received just yesterday (04/20/2013) from a non-profit organization seeking a donation. It's also curious that not only does the postage meter not contain a date, but no month or year, either.
USPS research suggests many similar rates but nothing that specifically meets the 14.6 cent rate. The nearest I can find is a 14.9 cent rate.
No big deal, just a postage rate I've never seen before. Any ideas?