Use material defines more

code/modules/paperwork/pen.dm

@@ -20,7 +20,7 @@
 	w_class = ITEMSIZE_TINY
 	throw_speed = 7
 	throw_range = 15
-	matter = list(DEFAULT_WALL_MATERIAL = 10)
+	matter = list(MAT_STEEL = 10)
 	var/colour = "black"	//what colour the ink is!
 	pressure_resistance = 2
 	drop_sound = 'sound/items/drop/accessory.ogg'

code/modules/paperwork/photography.dm

@@ -128,7 +128,7 @@ var/global/photo_count = 0
 	item_state = "camera"
 	w_class = ITEMSIZE_SMALL
 	slot_flags = SLOT_BELT
-	matter = list(DEFAULT_WALL_MATERIAL = 2000)
+	matter = list(MAT_STEEL = 2000)
 	var/pictures_max = 10
 	var/pictures_left = 10
 	var/on = 1

code/modules/paperwork/stamps.dm

@@ -9,7 +9,7 @@
 	slot_flags = SLOT_HOLSTER
 	throw_speed = 7
 	throw_range = 15
-	matter = list(DEFAULT_WALL_MATERIAL = 60)
+	matter = list(MAT_STEEL = 60)
 	pressure_resistance = 2
 	attack_verb = list("stamped")
 	drop_sound = 'sound/items/drop/device.ogg'