A letterhead or bookplate of "Camp Elsinore", summer home of <a href="https://en.wikipedia.org/wiki/Edward_Hornor_Coates" class="extiw" title="w:Edward Hornor Coates">Edward Hornor Coates</a> and <a href="https://en.wikipedia.org/wiki/Florence_Earle_Coates" class="extiw" title="w:Florence Earle Coates">Florence Earle Coates</a>.  This image was pasted into a copy of Mrs. Coates' <a href="https://en.wikisource.org/wiki/Poems_(Coates_1916)/Volume_I" class="extiw" title="s:Poems (Coates 1916)/Volume I"><i>Poems</i> Vol I</a> (1916) inscribed to <a href="https://en.wikipedia.org/wiki/Amos_Wilder" class="extiw" title="w:Amos Wilder">Amos Niven Wilder</a>.
<bdi><a href="https://en.wikipedia.org/wiki/en:Florence_Van_Leer_Earle_Coates" class="extiw" title="w:en:Florence Van Leer Earle Coates"><span title="American writer and poet (1850-1927)">Florence Earle Coates</span></a>
</bdi>
Early 1900's (pre-1908)
I own original image; photographer unknown. See description.