The 500 series of oscilloscopes from Tektronix includes:
531 - 10 MHz dual timebase scope
532 - 5 MHz scope
533 - 15 MHz scope
535 - 10 MHz dual timebase scope
536 - X-Y scope (no trigger/sweep)
541 - 30 MHz single timebase scope
543 - 30 MHz single timebase scope
544 - 50 MHz single timebase scope
545 - 30 MHz dual timebase scope
546 - 50 MHz single timebase scope
547 - 50 MHz dual timebase scope
549 - 30 MHz storage scope
551 - 27 MHz dual-beam scope
555 - 30 MHz dual-beam scope
556 - 50 MHz dual-beam scope
These scopes take letter-series and 1-series plug-ins.
