Muzzle and sight look legit, but that s/n is just not possible - that HAS to be a replaced receiver, or an "assembled" gun. It did NOT come out of the ORIGINAL assembly process (almost slipped up and said "down the line") as you see it today. Three choices:

1. A VERY unusual arsenal, or in-service, "repair"

2. An "in-house" Bubba

3. An outhouse Bubba (including Bannerman et al)

Back in the day, they were TOOLS - and when they were broken they were repaired -nobody cared about 21st century "collector originality".