Cal. 8L21 was an automatic watch movement produced by Seiko’s Shizukuichi Watch Studio for the Brightz brand from 2003 through 2007. It was based on the Grand Seiko Cal. 9S51 which was produced at the same time. The Prospex/Brightz Cal. 8L35 was similar but added a date complication.
Cal. 8L21 was used in the Brightz SAGL model line. This appeared in Seiko catalogs and the Seiko Japan website from 2003 through 2007.
| Production | Application | Winding | Jewels | Notes | |
|---|---|---|---|---|---|
| 8L21 | 2003-2007 | Brightz SAGL | Automatic | 24 | Similar to 9S51 |
| 8L34 | 2000 | Railway pocket watch | Manual | 20 | Small seconds |
| 8L35 | 2000-present | Brightz SAGQ Prospex SBDX Prospex SLA | Automatic | 26 | Date, similar to 9S55 |
| 8L36 | 2011-present | Credor GCBZ Galante SBLM | Automatic | 27 | GMT, similar to 9S56 |
| 8L38 | 2010-2015 | Galante SBLL | Automatic | 26 | Open Heart |
| 8L75 | -2005 | Credor GCBR | Automatic | 26 | Date, similar to 9S55 |
| 9S51 | 1998-2009 | GS SBGR | Automatic | 24 | No date |
| 9S54 | 2001-2010 | GS SBGW | Manual | 20 | No date |
| 9S55 | 1998-2010 | GS SBGR | Automatic | 26 | Date |
| 9S56 | 2002-2010 | GS SBGM | Automatic | 27 | GMT, no date |