diff --git a/STATUS.md b/STATUS.md
index 249ca2f9..d0f492f4 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -232,7 +232,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$BC0F`   | `mov_FAC1_FAC2`        | DONE     |                                                    |
 | `$BC1B`   | `round_FAC1`           | PARTIAL  | not fully tested yet                               |
 | `$BC2B`   | `sgn_FAC1_A`           | DONE     |                                                    |
-| `$BC39`   | `sgn_FAC1`             | NOT DONE |                                                    |
+| `$BC39`   | `sgn_FAC1`             | DONE     |                                                    |
 | `$BC3C`   | `convert_A_to_FAC1`    | PARTIAL  | not fully tested yet                               |
 | `$BC44`   | `convert_i16_to_FAC1`  | PARTIAL  | not fully tested yet                               |
 | `$BC58`   | `abs_FAC1`             | NOT DONE |                                                    |
diff --git a/src/basic/,stubs_math/bc39.interop b/src/basic/math/bc39.interop
similarity index 100%
rename from src/basic/,stubs_math/bc39.interop
rename to src/basic/math/bc39.interop
diff --git a/src/basic/,stubs_math/bc39.sgn_FAC1.s b/src/basic/math/bc39.sgn_FAC1.s
similarity index 90%
rename from src/basic/,stubs_math/bc39.sgn_FAC1.s
rename to src/basic/math/bc39.sgn_FAC1.s
index 7828f4e6..20be7ef3 100644
--- a/src/basic/,stubs_math/bc39.sgn_FAC1.s
+++ b/src/basic/math/bc39.sgn_FAC1.s
@@ -15,7 +15,6 @@
 ; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
 ;
 
-; XXX provide implementation
-
 sgn_FAC1:
-	+STUB_IMPLEMENTATION
+	jsr sgn_FAC1_A
+	; Fallthrough to convert_A_to_FAC1
diff --git a/strings/202BBC8562 b/strings/202BBC8562
new file mode 100644
index 00000000..f7af9b82
--- /dev/null
+++ b/strings/202BBC8562
@@ -0,0 +1,3 @@
+JSR $BC2B + STA $62
+
+Calls the SGN FAC1 into A which is a well known routine and then stores the result in the FAC1 mantissa. Trivial