The 870 lightweights on the 28/410 sized receiver were designated LW20 from the beginning in 1972. Every 870 was a Wingmaster before the first Expresses in 1987, although Remington marketed the Sportsman versions of the 1100 and 870 in the 80s that carried hardwood stocks and still had polished blued metal. They did not say 1100 or 870 on them. All current 870s and 1100s are on that same 28 sized receiver, although they have dropped the LW and LT designations.
The LW 20 Model 1100 was introduced in 1970, on the same sized receiver. Due to some issues it was revised and changed to the LT 20 design in 1977.
Remington also produced some guns in both series in the 1960s that they built on the 12 gauge sized receivers, that they called lightweights, because they equipped them with mahogany stocks and fore ends. There was no rollmarking on the metal to identify them that I have ever seen.
Remington rollmarking is not reliable for positive identification I don't think. I have seen an 1100 with nothing but a serial number on it anywhere, and apparently the guy (or gal) who date codes the barrels has no one to fill in when they aren't there.
Remington Serial # suffixes:
V 12 GA. (2 3/4”)
M 12 GA. MAGNUM (3”)
A 12 GA. “SUPER” MAGNUM (3 ½”)
W 16 GA. ( 2 ¾” )
X 20 GA. “HEAVY FRAME” (DISCONTINUED)
N 20 GA. “HEAVY FRAME MAGNUM” (DISCONTINUED)
K 20 GA. “LIGHT WEIGHT” (“LW”) (ALSO INCLUDES M/1100 “LT”)
U 20 GA. LW MAGNUM (ALSO INCLUDES M/1100 “LT”)
J 28 GA.
H .410 BORE (2 ½” OR 3”)
