Otto,
I hate to disagree with you, since you are usually 90% correct, but some railroads had thier own profiles, thus the RR Co name was imprinted. Case and point, NYNH&H 107#. If you look at any 107# rail, at least from Beth Steel, it is marked 107 NH or 100 NH on some of the earlier ones. The 107 profile was the standard 100# rail with a thicker head.
Writing this just got me thinking, so I just checked a book I have in my collection, `Practical Trackwork, Swich Stands, Switches, Frogs, Crossing and Slip Switches' witten in 1928 by Walter F. Rench. In the back it has 3 double page charts of track sizes, the first page is the standard sizes: ASCE, ARA-A, ARA-B, & AREA, but the other 2 are all railroad specific sizes (or at least has a RR Co in the name) It also lists which company used what marking per size. The companies shown are Illinois Steel Co/Carnegie/TC&I Co, Bethlehem Steel Co, Colorado/F&I Co, and Inland Steel Co. Between the weight and comany numbers, it also list all the measurments, that define the specific profile.
Type..............|....#...|...Carnegie...|..Beth Steel..|..Colorado...|..Inland
AT&SFe..........|...90...|......9021......|....90-SF.......|.....903.......|...9021
Bang & Aroos..|..70....|...................|...70-BA.......|..................|.........
Can Nor..........|..80....|.....8010.......|.....804........|..................|.........
Can Pac..........|..85....|.....8524.......|...85-CP.......|..................|.........
...
NYNH&H..........|..107..|....10734......|...107-NH......|..................|.........
NYNH&H..........|..100..|....10034......|...100-NH......|..................|.........
Also there is an amount more as you can guess, but I didn't see any 1000, 100010 indications, but I would agree with Otto, that LS&Co would be Lackawanna Steel, before they became part of Beth Steel. This is even more evident after looking online and finding out that LS&Co's second plant was in Buffalo, built 1899-1900.
Take care,
Rich