After 1908, probably before 1915.
There are several things to note here:
- The new(ish) coat closing style only. Pull-over shirts are available right through the 1930s and some patterns at this period offer both options, but for this pattern only the coat closing option is given.
- The extremely helpful chart showing chest measurements corresponding to the neck measurements.
- The layout showing the largest size (18" neck) laid out on 36" wide goods. Note the piecing of the sleeve (S) and the collar stand (R.)
- The method of attaching the sleeve to the shirt body, in which the sleeve seam allowance is turned under and then fitted onto the body. This allows the sleeve to be sewn on from the outside for greater accuracy. This same technique is used when tailoring men's coats, and was used on the slightly earlier Cosmopolitan Outing Shirt.
- The collar stay made up of a short length of tape with buttons sewn to it. The button holes worked in the collar are then buttoned to this stay, and it appears the (very narrow) tie lies in front of it.
- The somewhat bizarre suggestion that in addition to the yardage for the shirt, one will need to get "1 Tie."
Note that the instructions are quite brief. You're expected to make your own decisions regarding interlining, seam finish, and hip gussets.
This unprinted pattern appears to be in factory folds and was an eBay find for a whopping $3.99. These early shirt patterns do show up periodically and usually go pretty reasonably. A 14 1/2" neck is on the small side, which may have been why there wasn't more competition for this one - I was the only bidder.