Single 0x03/0x83 is too weak (the first conflicts with Python 2.7);
rely on the fact, that third byte is the last modification month in BCD, i.e. <= 0x12
--- file-5.04/magic/Magdir/msdos.orig	2010-08-25 08:34:47.942823295 +0200
+++ file-5.04/magic/Magdir/msdos	2010-08-25 09:04:06.554822457 +0200
@@ -549,12 +549,14 @@
 0	lelong		0x08084b50	TurboC Font file
 
 # WARNING: below line conflicts with Infocom game data Z-machine 3
-0	byte		0x03		DBase 3 data file
->0x04	lelong		0		(no records)
->0x04	lelong		>0		(%ld records)
-0	byte		0x83		DBase 3 data file with memo(s)
->0x04	lelong		0		(no records)
->0x04	lelong		>0		(%ld records)
+0	byte		0x03
+>0x02	byte		<0x13		DBase 3 data file
+>>0x04	lelong		0		(no records)
+>>0x04	lelong		>0		(%ld records)
+0	byte		0x83
+>0x02	byte		<0x13		DBase 3 data file with memo(s)
+>>0x04	lelong		0		(no records)
+>>0x04	lelong		>0		(%ld records)
 0	leshort		0x0006		DBase 3 index file
 0	string		PMCC		Windows 3.x .GRP file
 1	string		RDC-meg		MegaDots