This is my first example of Paul Mortensen using a straight text mark, rather than the curved text with the curlicue. I also have an example of that style from this year, suggesting that he adopted it during 1928.
This one makes me happy in a confused way, pushing this version of the Fitzmaurice mark (version III) back three years. As far as I can tell, this was used entirely within the period that version II was used.