Both of your Model 99s SHOULD have Lever Boss Codes ("LBC")... 543126 was probably manufactured in late 1949 or early in 1950. The LBC for 1949 is "A" with the LBC for 1950 is "B". Use a magnifying glass to inspect the LBCs... they should appear as a number (the inspector's number) followed by a letter indicating the year-of-manufacture... with both the inspector's number AND the LBC letter INSIDE an OVAL (not a circle) which is VERY lightly embossed on the lower, front side of the receiver near the bolt on which the lever rotates. Here is an excerpt from my records for your older Model 99.
A= 1949: 519540, 530233(26A), 533399(A),
B= 1950: 531909(15B), 5502xx(24B),555436(?B), 561xxx(24B),575495(21B), 572777(15B), 58021X(15B), 582xxx (24B),584xxx(15B)
Your newer Model 99 (A314977) was probably manufactured in 1969 and has a "W" Lever Boss Code or in 1970 with an "X" Lever Boss Code. Here are excerpts from my records indicating the LBCs and year-of-manufacture. You can see where your rifle's serial number falls... possibly in late 1969 or early in 1970.
W= 1969: A009045 (Jan), A226071 (June), A279775, A296xxx,
X= 1970: A387575 (Jan), A389783 (very early 1970) A652xxx (Nov),
I hope this helps...
Strength & Honor..
Ron T.