Toshiba makes many CF cards for themselves and third parties. If your CF edge stamp is "THNCF1G02MA" then it has a very slow write speed compared to Ridata 256 52x (by more than 60%). However if the edge stamp serial is "THNCF512MCA" or "THNCF1GB02CA" then this card is faster than Ridata 52x by 10% and 80% compared to "THNCF1G02MA". I know some of the latest Kingston CF are using this.
Again, if you are using normal digicam, it doesn't really matter that much. But speed matters a lot with higher megapixel prosumer and DSLR.