Reach catalogs pictured Lajoie, amongst other players, but this is the first actual glove endorsement from him I've encountered. Doesn't necessarily mean that there were Lajoie stampings on actual gloves, but we can only hope! Even a hang tag, as Joe said, would be stupendous. Many early 1900's catalogs had player signatures on gloves in print advertisements that weren't on the actual gloves. Teen's Stall & Dean catalogs are perfect examples. Yes, I remember that fake Lajoie glove fiasco well from the mid-1990's... ah, the early days of eBay, it was like the wild west!
Brett alluded to the lack of webbing. There has been debate in the hobby for several years over the term "workman". Here's an example of this debate;
viewtopic.php?f=10&t=1155&hilit=workmanNow, a subsequent debate falls on the "type" of glove shown in the Lajoie ad. For years, many (mostly sellers trying to extract more out of a price) called this design a "workman". Some agreed, some disagreed but most just went along with it and assumed it was because so few true "workman's" gloves exist, they had nothing to compare it with. I've been in the camp that this design is not a "workman" and it was manufactured after 1900. This Lajoie ad does not prove anything one way or the other, but it does help strengthen the case that this "type" of glove is not form the 19th century and should not be considered a "workman's" glove in the true sense of the term and description. In my opinion, it's simply a webless glove from the early part of the 20th century which does not pre-date crescents. It was produced concurrent with webbed crescents, but crescent shaped padding, especially webless crescent, came first.