With regard to your photograph, it probably was taken by A.B. Paine.
Paine was an excellent portrait photographer, and I know that he worked
with a 5x7 stereo camera, because I have seen (and own) images
contact-printed from the negatives. He also worked with non-stereoscopic
cameras, but I have seen no commercial prints made from them.
The view that you describe sounds like the classic stereoview of SLC
that was sold by Underwood and Underwood (U&U), a commercial publisher
of stereoscopic and other photographs. There also were stereoviews of
SLC sold by White & White and the Keytone View Company in ~ 1905 - 1910,
and therafter. One wonders if there were some kind of royalty paid to
SLC from the use of his image, although given the times, I would guess
that there was not.
U&U was then only beginning to get into the newspaper file-photo
supplying business. They covered the world and furnished
newspaper-subscribers with 5x7 and 8x10 real photos of people and places
that were filed and retrieved when the image would be useful for an
article. Typically there is an inked-stamp on the reverse saying:
"Please credit Underwood and Underwood...". Their photos became
increasingly more common throughout the 20s and 30s. I have seen (both
copy and original contact-print) photos taken in the 'teens that clearly
were made for 1930's press releases.
It is unusal to see commercial real-photos of SLC from this era in other
than the stereoview-format. The Gallagher-publisher alongside the U&U
copyright is a curiosity; I've not seen the like. One cannot be sure of
when the print were made; one clue could be the type of frame in which
the image is encased. I probably could help date the time-of-printing by
the kind of paper used, and how the finish appears. Perhaps there is a
dealer in vintage photography in your environs who could help more
directly than I, who resideth in faraway Cincinnati.
It is an interesting image, and if you wish, I'ld be glad to correspond
privately and help you try to date when it could have been made. If it
were a copy-print, it should be easy to tell, because they are never as
sharp. If it were an original image made around the time of the original
negative, it could be valuable.
Hope that this helps,