I was going to go off of the top of my head on the account of me being a lazy bastard, but I will just cut and paste:
1934:
Mauser, Obendorf- S/42K
J.P Sauer, Suhl- S/147K
1935:
Mauser, Obendorf- S/42G
J.P Sauer- S/147G ERMA- S/27G
Mauser, Borsigwalde- S/243G
1936:
Mauser, Obendorf- S/42 above date 1936
J. P. Sauer- S/147 above date 1936
ERMA- S/27 above date 1936
Mauser, Bosigwalde- S/243 above date 1936
Berlin-Lubecker- S/237 above date 1936
1937:
Mauser, Obendorf- S/42, 1937
J. P. Sauer- S/147, 1937
ERMA- S/27, 1937
Mauser, Borsigwalde- S/243, 1937
Berlin-Lubecker- S/237, 1937
Berlin-Suhler-Waffen (BSW)- BSW, date 1937
1938:
Mauser, Obendorf- S/42 1938, and also "42" 1938
J. P. Sauer- S/147 1938, and also "147" 1938
ERMA- S/27, 1938, and also "27" 1938
Mauser, Borsigwalde- S/243 1938, and also "243" 1938
Berlin-Lubecker- S/237 1938, and also "237" 1938
BSW- BSW 1938
1939:
Mauser, Obendorf- "42" 1939
J. P. Sauer- "147" 1939 and also no date or code!
ERMA- "27" 1939
Mauser, Borsigwalde- "243" 1939
Berlin-Lubecker- "237" 1939
BSW- BSW 1939, and also combined with Gustloffwerke for "337" 1939
Steyr- Daimler, Steyr- "660" 1939
1940:
Mauser, Obendorf- "42" 1940
J. P. Sauer- "147" 1940
ERMA- "27" 1940, and also "ax" 1940
Mauser, Borsigwalde- "243" 1940
Berlin-Lubecker- "237" 1940, and also "duv" 40 date.
Gustloffwerke- "337" 1940 Steyr- "660" 1940, and also "bnz" 40 date.
1941:
Mauser, Obendorf- "byf" 41.
J. P. Sauer- "ce" 41
ERMA- "ax" 41
Mauser, Borsigwalde- "ar" 41
Berlin-Lubecker- "duv" 41
Gustloffwerke- "bcd" 41
Steyr- "bnz" 41
1942:
Mauser, Obendorf- "byf" 42
J.P. Sauer- "ce" 42
Mauser, Borsigwalde- "ar" 42
Berlin-Lubecker- "duv" 42
Gustloffwerke- "bcd" 42
Steyr- "bnz" 42
Waffen Werke Brunn, Bystrica- "dou" 42
1943:
Mauser, Obendorf- "byf" 43
J. P. Sauer- "ce" 43
Mauser, Borsigwalde- "ar" 43
Gustloffwerke- "bcd" 43
Steyr- "bnz" 43
Waffen Werke Brunn, Bystrica- "dou" 43
Waffen Werke Brunn, Brunn- "dot" 43
1944:
Mauser, Obendorf- "byf" 44
J. P. Sauer- "ce" 44
Mauser, Borsigwalde- "ar" 44
Gustloffwerke- "bcd" 4
Steyr- "bnz" 44 or "bnz" 4 *
Waffen Werke, Brunn, Bystrica- "dou" 44 *
Waffen Werke, Brunn, Brunn- "dot" 1944 *
1945:
Mauser, Obendorf- "byf" 45 * /**
Mauser, Obendorf- "svw" 45 */ **
Mauser, Obendorf- "svw" MB **
Gustloffwerke- "bcd" 45 * Steyr- "bnz" 45 *
Waffen Werke Brunn, Bystrica- "dou" 45 *
Waffen Werke Brunn, Brunn- "swp" 45 *
*- Later (higher) serial numbers were issued as Kriegsmodells.
**- Kriegsmodells had rough unfinished stocks and no butt plate. Some years may have dual maker codes and/or dual dates marked on receiver.
I got the above information from the "nazarian" website or whatever. Google it and you should find it. Just make sure you don't end up at Stormfront.
I own a 1943 "DOU" code. It is a semi-kriegsmodell with no bayonet lug. It has a terrific bore and last week at the chabot get together with a few calguns.net members (including the soup nazi) I was hitting the black from 100 yards with no problem. I fired 10 rounds for accuracy (surplus romanian 8mm) and most of it grouped around 1.5 MOA between the 9 and 10 ring. Whatever you do, get one with a bore that has NO pitts. Do not pay more than $350 for one that was captured by the Russians. There will be an X marked somewhere on the receiver to show this. Try to get one that has the nazi proof marks (waffenamts) not pinged out. Almost all of RC 98ks will have electropenciling on them.
Pictures:
I have since taken the scope off. The grouping I was talking about above was with open sights. I need to get a dial caliper to get the mount on just right or else the thing will come loose (it is a no drill/no tap job) which it has on multiple occassions.