How to transcribe sin (or shin) as  an initial when you're not sure what Hebrew name it stands for?
 
Segev, Si'on, Si'el, Salmon, Simhah, etc.  are examples of  names that  begin  with  sin.   Even  though cyrillic  does distinguish
between "s"  and "sh", it doesn't really prove whether the Hebrew is  sin  or shin, since one can't know whether or  not the author used a completely different name in Russian (?).
 
In  any case,  if  you don't  know whether sin  or  shin  is involved, assume  a  shin  for  the  purposes  of formulating the
heading, make a reference from the form which assumes a  sin, and code the heading as provisional.