Invoking the Tsurugi of Muramasa when it has enchantment less than 0 (or -1 if cursed, or 1 if blessed) changes its enchantment to 0 (or -1 if cursed, or 1 if blessed).

diff -Nurb nethack-3.4.3-original/dat/Samurai.des nethack-3.4.3-copy/dat/Samurai.des
--- nethack-3.4.3-original/dat/Samurai.des      Mon Dec  8 09:39:12 2003
+++ nethack-3.4.3-copy/dat/Samurai.des  Tue Oct 25 22:57:41 2005
@@ -277,7 +277,7 @@
 # Non diggable walls
 NON_DIGGABLE:(00,00,44,19)
 # Objects
-OBJECT:')',"tsurugi",(22,10),blessed,0,"The Tsurugi of Muramasa"
+OBJECT:')',"tsurugi",(22,10),blessed,1,"The Tsurugi of Muramasa"
 OBJECT:random,random,random
 OBJECT:random,random,random
 OBJECT:random,random,random
diff -Nurb nethack-3.4.3-original/include/artifact.h nethack-3.4.3-copy/include/artifact.h
--- nethack-3.4.3-original/include/artifact.h   Mon Dec  8 09:39:13 2003
+++ nethack-3.4.3-copy/include/artifact.h       Fri Oct  7 13:48:47 2005
@@ -60,5 +60,6 @@
 #define CREATE_PORTAL  (LAST_PROP+7)
 #define ENLIGHTENING   (LAST_PROP+8)
 #define CREATE_AMMO    (LAST_PROP+9)
+#define SHARPEN                (LAST_PROP+10)
 
 #endif /* ARTIFACT_H */
diff -Nurb nethack-3.4.3-original/include/artilist.h nethack-3.4.3-copy/include/artilist.h
--- nethack-3.4.3-original/include/artilist.h   Mon Dec  8 09:39:13 2003
+++ nethack-3.4.3-copy/include/artilist.h       Fri Oct  7 13:47:09 2005
@@ -210,7 +210,7 @@
 A("The Tsurugi of Muramasa",   TSURUGI,
        (SPFX_NOGEN|SPFX_RESTR|SPFX_INTEL|SPFX_BEHEAD|SPFX_LUCK), 0, 0,
        PHYS(0,8),      NO_DFNS,        NO_CARY,
-       0,              A_LAWFUL, PM_SAMURAI, NON_PM, 4500L ),
+       SHARPEN,        A_LAWFUL, PM_SAMURAI, NON_PM, 4500L ),
 
 #ifdef TOURIST
 A("The Platinum Yendorian Express Card", CREDIT_CARD,
diff -Nurb nethack-3.4.3-original/src/artifact.c nethack-3.4.3-copy/src/artifact.c
--- nethack-3.4.3-original/src/artifact.c       Mon Dec  8 09:39:13 2003
+++ nethack-3.4.3-copy/src/artifact.c   Fri Oct  7 14:36:29 2005
@@ -1349,6 +1349,20 @@
                                       aobjnam(otmp, "fall"), (const char *)0);
            break;
          }
+       case SHARPEN: {
+          int sharpnum = (obj->cursed ? -1 : (obj->blessed ? 1 : 0));
+
+          if (obj->spe >= sharpnum) {
+               pline("%s is %ssharp enough already.", The(xname(obj)), 
+                   (obj->spe > -1 ? (obj->spe > 0 ? "more than " : ""): "almost "));
+               obj->age = 0;
+               return 0;
+          }
+          obj->spe = sharpnum;
+          pline("%s is restored to %sits original keenness!", The(xname(obj)),
+               (obj->spe > -1 ? (obj->spe > 0 ? "better than " : ""): "slightly less than "));
+          break;
+         }
        }
     } else {
        long eprop = (u.uprops[oart->inv_prop].extrinsic ^= W_ARTI),