Looks very genuine.
LMT bolts have had a variety of different letter stamped into them . . .I forget them all . . .F, E, etc...
The brass marks are from test firing.
LMT had a batch of their standard bolts nickel plated (like their enhanced model) instead of parkerized
My guess is the nickel was a mistake (an upgraded mistake), but it is not a standard item. . . . unless they have a new offering now?