The Silver series has gone through numerous model lineups over the years. The newest ones are just called Silver 1/2/6/8/10. The previous series was the RX series (RX1, RX2, RX6, RX8).
Here's a rough history of the Silver series:
Silver S series
S1, S2, S6, S8, S10
Silver RS series
RS1, RS6, RS8 (no RS2, no RS10)
Silver RX series
RX1, RX2, RX6, RX8
Silver 1, Silver 2, Silver 6, Silver 8, Silver 10
For every new thing I learn, I forget two things I used to know.