there is a single screw on the reverse side, center of the black plastic grill... once you have the front bumper off, everything becomes more apparent.
along with the single screw, there are clips holding the assembly into place...
Some additional information can be found at...http://plaza.umin.ac.jp/~satoshi/mod017en.html
Thank you Satoshi from Japan!
More photos at...https://www.celicahobby.com/photos/celica/installs/inst_front-bumper-badge/