The NC-303 had a number of accessories. The NCS-2 speaker is the matching speaker for the NC-303. I have never seen one but I am continuing to look (I guess that is what collecting is about - the Quest). As previously mentioned, the NC-303 had a number of companion converters sold optionally NC-300-C1 for 1.25 meter operation, NC-300-C2 (pictured below) for 2 meter operation and the NC-300-C6 for 6 meter operation. National also manufactured a combo speaker and converter cabinet that mounted the three converters. The picture immediately to the right is the XCU-303 crystal calibrator. This device is a little different from crystal calibrators from other receivers. The 10 MHz WWV spot uses the 1000 harmonic of the 100 kHz marker oscillator to derive the 10 MHz for reception. National Speakers.