Many undivided cards of this firm bear the full company name rather than a logo. Later, many divided cards (eg in the 1920s) show just the initials J. S. & Co. M or J.S.u.Co.M.
An article on this company has appeared in The Postcard Annual no 34, which gives details about the firm. It also reveals that Gerhard Stummp, in his book "Halt gegen Licht" (ISBN 978-3-938543-3), shows that Silberstein had used a shorthand version of his name as a logo on some hold-to-light cards. These cards are covered "here".