@ddcnga , the Ogden, UT service center address is :
Department of the Treasury
Internal Revenue Service
Ogden, UT 84201
There is often a zip code extension for some specific forms/information request. The "OSC" stands for Ogden Service Center.
I think your CP-12 is legitimate and therefore the return address is legit.
You can also visit your local IRS office ( usually in the local federal building ) to confirm.
