I have no 423 and it is marked 30 GOVT 06. It has the service barrel with sight spline cut. If I recall correctly, Petrovs s/n sequencing explanation would have these guns in the early-mid 1924 era. The first numbers being non-caliber related, next were specific blocks of numbers according to chambering (like these in the 400 series all being 30-06), then back to sequential regardless of chambering.

Certainly the golden age of American rifles