1917 eddystone

[Patrick Chadwick]

According to Ferris, P87: 3 recorded examples of 129xxxx, all with November 1918 barrels.
One example, 1290089 is max. 2 days away from your rifle, assuming steady rate of production.

Take a close look at the top end of the barrel, there should be an "11-18" stamped there. Stamp can be faint, so you may need to turn the barrel around to catch the light at varying angles.