Hi, I've been collecting Horner pieces for 5 or 6 years. I don't have an online reference for his trademark (this site only includes one of his many maker's marks), but he registered the intertwined CH (no. 367836) in 1915 per Tom J. Lawson's book
Charles Horner of Halifax - a Celebration of his Life and Works, page 36.
On page 92 of the book, there is an image of a pendant quite similar to John's. In addition, I have a ring in my personal collection that is pictured in the book (p. 98) that has the same marks (unfortunately a bit rubbed):
Unfortunately, I no longer have the citation for Hemming, but over the years, I picked up a few pieces online hoping they were unrecognized Horner pieces. Alas, after handling several of them, it became obvious that it was indeed a different maker.I learned that Hemming Manufacturing Company was in operation in Montreal, Canada, from 1909-1916.
Although both companies produced sterling and enamel jewelry, the manufacture, construction and quality are different. I have only seen brooches and pins by Hemming, whereas Horner produced necklaces, rings, buttons, etc. If you compare the pins, you will note that Horner's c-clasp was a simple curled wire design, while Hemming had a wider, flat, folded metal clasp.
Hemming produced many pieces with Canadian motifs, with the larger pieces featuring various city crests, and smaller ones often with the maple leaf. The technique of the enamel is also different from Horner. Here are some examples of Hemming's work (along with pics of the marks):
