I believe it's a POBox for several reasons. I couldn't find proof for this exact address, but here are my reasons for thinking this.
The zip code Plus 4 matches when it's a P O Box. In this case, #230912 matches the zip code Plus 4 (the last six numbers). 89123-0912. This happens quite often, like for credit card bills or other businesses.
Although "P. O. Box" is the preferred use, "#" is sometimes used. I saw this point made in some websites about P.O. Boxes.
There is a post office at 455 E Pebble Road.
On Google Maps, I see that the address has a building, but I don't see evidence of other offices in there. 230912 is too large for a unit number for a small building, although not impossible, I guess.
Always be on guard for misleading, deceptive or erroneous messages. I am not an investment professional. My messages are my opinion only, and are subject to change when contrary information is later relied upon. Always do your own research.