Negatively stained catalase crystals show lattice plane spacings of approximately 8.75nm and 6.85nm very clearly (using TEM and STEM). (Figures determined by Wrigley. J. Ultrastructure Res. 24, 454. 1968).
They are valuable for high magnification calibration.
For higher magnifications, one of the crystal lattice plane specimens can be used. See AGS140 or AGS135.