TDK labels Mitsui, Taiyo Yuden, Moser Baer and other CD media here as well, not just Ritek .
The new TDK 52x “reference” discs (light-blue package) are high quality Mitsui discs. My Plextor Premium and NEC ND-3500A don’t have the lowest error rates with these discs (not as low as TY, but still low; both can burn them at 52x and 48x respectively), but the quality of the discs itself is awesome (extra protective layer, nice finish and great looks). They have the extra robust Mitsui phthalocyanine type 8 dye, which should guarantee longevity as well.
This is how the spindles look like:
P.S.: Original TDK CD media is very rare over here now, too. TDK media used to be absolutely fantastic, especially in the beginning of the CD burning era. This is a scan of a TDK Reflex 650MB disc I did recently.
The disc was burned at 4x on August 6th 1998, over 6 years ago, with a Yamaha 400t CD burner.
Plextools 2.17 C1/C2/CU Scan with Plextor Premium drive:
Such low error rates (as low as the best TY discs today) after 6 years is just amazing.