All 16 chalk writing texts, from textures\decals\ptest\chalk_maze_writing.
http://i.imgur.com/nTjIL.png
All of the chalk heiroglyphs:
All of the chalk letters:
And here are all of the maps that grep positive for ptest:
./ch01/00_rainy_hall.map:151: <File Id="2" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />
./ch01/00_rainy_hall.map:152: <File Id="3" Path="textures/decals/ptest/chalk_letters.mat" />
./ch01/03_archives.map:197: <File Id="4" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />
./ch01/06_distillery.map:156: <File Id="8" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />
./ch01/06_distillery.map:157: <File Id="9" Path="textures/decals/ptest/chalk_letters.mat" />
./ch01/07_archives_cellar.map:101: <File Id="0" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />
./ch01/11_study.hps:225: PlaySoundAtEntity("phono_scrape", "ptest_phono_loop", sEntity, 1.0f, false);
./ch01/11_study.map:219: <File Id="156" Path="entities/ptest/phonograph/phonograph.ent" />
./ch01/11_study.map:226: <File Id="4" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />
./ch02/17_control_room.map:131: <File Id="4" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />
./ch02/22_torture_chancel.map:176: <File Id="3" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />
./ch02/22_torture_chancel.map:177: <File Id="4" Path="textures/decals/ptest/chalk_letters.mat" />
./ch02/22_torture_chancel.map:178: <File Id="5" Path="textures/decals/ptest/chalk_maze_writing/chalk_maze_writings16.mat" />
./ch03/26_torture_nave_redux.map:265: <File Id="12" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />
./ch03/27_torture_chancel_redux.map:167: <File Id="4" Path="textures/decals/ptest/chalk_hieroglyphs.mat" />