fcc info on 170.475 etc

(8) US8 The use of the frequencies 170.475, 171.425, 171.575, and
172.275 MHz east of the Mississippi River, and 170.425, 170.575,
171.475, 172.225 and 172.375 MHz west of the Federal Communications
Commission 274 Mississippi River may be authorized to fixed, land and
mobile stations operated by non-Federal forest firefighting agencies.
In addition, land stations and mobile stations operated by nonFederal
conservation agencies, for mobile relay operation only, may be
authorized to use the frequency 172.275 MHz east of the Mississippi
River and the frequency 171.475 MHz west of the Mississippi River. The
use of any of the foregoing nine frequencies shall be on the condition
that no harmful interference will be caused to Government stations.

from https://www.fcc.gov/sites/default/files/fcctable.pdf