Felix Sater's LinkedIn profile details his starting work for Regency Capital as far back as what would have been his time in Russia, January 1998.  On LinkedIn, he listed it as Regency Investment Group but as you can see under his picture it is Regency Capital Group.  It may be referred to as both.  Note it is only within a little over a year following the start of Regency, he's working with Bayrock and Tevfik Arif. 

 

(His FBI cooperation agreement was signed December 1998.)