Crown Prince Constantine and Sophia of Prussia, by an unknown photographer, September 1888, from the Digital Commonwealth - commonwealth 6108xw169.
Unknown author<span style="display: none;">Unknown author</span>
Digital Commonwealth (<a rel="nofollow" class="external free" href="https://www.digitalcommonwealth.org/search/commonwealth:6108xw169">https://www.digitalcommonwealth.org/search/commonwealth:6108xw169</a>)