diff --git a/bin/ka10/_/@.mark b/bin/ka10/_/@.mark
deleted file mode 100644
index b80b0944..00000000
Binary files a/bin/ka10/_/@.mark and /dev/null differ
diff --git a/build/misc.tcl b/build/misc.tcl
index 3522abc2..4b928627 100644
--- a/build/misc.tcl
+++ b/build/misc.tcl
@@ -68,6 +68,10 @@ expect ":KILL"
 respond "*" ":midas;324 dsk0:.;@ sysgen_syseng; system gen\r"
 expect ":KILL"
 
+# mark
+respond "*" ":midas;324 dsk0:.;@ mark_syseng; mark\r"
+expect ":KILL"
+
 respond "*" ":midas sys3;ts syslod_sysen1;syslod\r"
 expect ":KILL"
 
diff --git a/src/syseng/mark.1 b/src/syseng/mark.1
new file mode 100644
index 00000000..283dcec4
--- /dev/null
+++ b/src/syseng/mark.1
@@ -0,0 +1,102 @@
+TITLE MARK TAPE
+
+;Reconstructed in 2020 by lightly editing SYSTEM GEN to match @ MARK
+;binary.
+
+MACLOD=37726
+
+A=1
+D=2
+B=3
+C=4
+P=5
+
+
+BEG:	CONO 635550
+TRY:	CONO UTC,203410
+	CONSZ UTS,2000
+	JRST .-1
+	CONSZ UTS,4
+	JRST TRY
+	CONO UTC,221410
+	CONO DC,3410
+	MOVEI B,2700.
+	MOVE A,[707707707707]
+END1:	BLAT
+	SOJG B,END1
+	MOVEI C,1102
+BLK:	MOVE A,[(70707)70770]
+	BLAT
+	MOVE A,[(77070)7000]
+	BLAT
+	HRLI A,7000
+	BLAT
+	HRRI A,-1000
+	BLAT
+	MOVEI B,175
+	HRLI A,-1000
+	BLAT
+	SOJG B,.-1
+	HRRI A,-701
+	BLAT
+	HRLI A,-701
+	BLAT
+	HRRI A,707007
+	BLAT
+	MOVE A,[(700707)70707]
+	BLAT
+	SOJG C,BLK
+	MOVE A,[70070070070]
+	MOVEI B,2700.
+END2:	BLAT
+	SOJG B,END2
+
+TRY2:	CONO UTC,202510
+	CONSZ UTS,2000
+	JRST .-1
+	CONSZ UTS,4
+	JRST TRY2
+	CONO UTC,233510
+	CONO DC,3410
+	MOVEI B,1101
+	MOVEI C,1
+LUP:	MOVEI A,0
+	CAIN C,1
+	MOVE A,B
+	CAIE C,2
+	CAIN C,203
+	MOVE A,234
+	CAIN C,3
+	MOVEI A,77
+	CAIN C,204
+	JRST COMP
+WR:	BLAT
+	SOJG C,LUP
+	MOVEI C,204
+	SOJGE B,LUP
+	CONSZ UTS,40
+	JRST .-1
+
+	CONO UTC,3000
+	CONSZ UTS,2000
+	JRST .-1
+	JRST TRY
+
+WA:	CONSZ UTS,6
+	JRST DING
+	CONSO DC,1000
+	JRST WA
+	DATAO DC,A
+	JRST (P)
+DING:	DATAO TTY,BELL
+	CONO UTC,1000
+	JRST 4,BEG
+BLAT=JSP P,WA
+COMP:	MOVE D,B
+	ROT D,-3
+	REPEAT 3,[ROTC A,3
+	ROT D,-6
+]	ROTC A,27.
+BELL:	SETCAI A,7
+	JRST WR
+	END BEG