Everything I can find on the rifle has the little LB stamped on it including the bolt head,it also has a #1 bolt head,the only part on the rifle with no LB is the front barrel band and it has the Savage stamp S on it.

The actual serial # is 18L6XXX which is stamped on the receiver just under the safety lever. It actually says on the side of the receiver.

No 4 Mk 1*
Long Branch
1942

I haven't bought the rifle as of yet just checking out some details and trying to learn what I can about it,I can get it for $125 if I decide I want to keep it.