Markings on muzzle

[4V50 Gary]

Saw a Leman rifle today which had these markings on the muzzle:

W.S.S.

1156

US

Thoughts on its meaning?

 

[4V50 Gary]

I've corresponded with a couple of knowledgable people in the CiviL War era and bothsuggested that it could be (Birge's) Western Sharp Shooters (14 Missouri aka 66th Illinois).