Mystery Sign

A collection of questions from previous AP exams includes some
formulae with a symbol unfamiliar to me. For example:

     D <equals-sign-with-dots-to-upper-left-and-lower-right> 2 log10 B

Google found only a single reference to
<equals-sign-with-dots-to-upper-left-and-lower-right> in an online
bulletin board comment indicating it means "approximately or equal".

(Japanese fonts actually have a character for
<equals-sign-with-dots-to-upper-left-and-lower-right>.)

Anyone know anything about this sign?