SM rolls were made by Felix Schüller in Leipzig.  The initials "SM"
stand for "Schüller-Musikrollen", as can be seen in an original advert
at http://www.faszinationpianola.de/notenrollen/typologie-der-notenrollen/1733539eae08bb633/d003.html 

You can read more about the company on the website of the
Excellent Grassi Music Instrument Museum at Leipzig University,
https://mfm.uni-leipzig.de/hsm/detail.php?id=81 

The rolls themselves never give any indication of who made them -
they just have a logo of SM with a crown above it, which has given
rise to various imaginative provenances.  It's clear that until recent
times few had access to the adverts in trade publications (such as
Zeitschrift für Instrumentenbau) that gave the real details.
	
The SM output was always described as hand-played, and some rolls
carry facsimile signatures.  I have a few of these rolls.  One familiar
signature is Michael Zadora who recorded extensively for Hupfeld (also
based in Leipzig).  One or two others you can have a guess at, the
rest aren't intelligible to me and don't duplicate Hupfeld or Welte
names.  They probably couldn't compete with the Hupfeld and Welte
budgets for famous artists. I've never seen a catalogue for SM.

Weirdly, Ord-Hume suggests that SM created 88-note renderings of
Welte-Mignon rolls -- this in almost certainly nonsense!

And, in a similarly imaginative way, MMD 200301 erroneously stated
that SM rolls were produced by Choralion in Berlin (the Berlin Aeolian
operation) -- Choralion didn't make rolls but sold re-labelled
Aeolian rolls made in the USA or the UK, standard Themodist rolls.

Julian Dyer