Seiko, along with Citizen, Casio, Armitron, etc., made many of ana-digi models 20+ years ago. It was a very popular style. Without more information it's going to be diffiult to pin the model number down. Have you tried googling the brand, searching Ebay or the sales forums on SCTF and WUS? Here's a link to a Silverwave for sale that I found.
http://forums.watchuseek.com/showthread.php?t=108451
http://forums.watchuseek.com/showthread.php?t=108451
