15429x when made ?

i'm loaned brother's 1911, i encouraged him to join NRA and then DCM
around 40 years ago he got this 1911 from the CMP.
rt frame- No 15429x, SA.
rt slide- Model of 1911. U. S. Army.
left slide- Patented APR 20. 1897. SEPT. 9. 1902 DEC. 19. 1905 FEB. 14. 1911., AUG. 19. 1913 Colt's PT. F. A. MFG. CO HARTFORD, CT. U.S.A. rearing colt in center.
left frame- UNITED STATES PROPERTY
parkerised finish, backstrap lanyard loop, plastic grips. very litttle internal wear, tiny scratches on outside.

Colt serial number 15429X was shipped May 29, 1917 to U.S. Expeditionary Forces, Hoboken, N.J. Quite a few of the NRA/DCM pistols were Model 1911's fresh from overhaul.

thank you.