I think the first version had no warc bands & was only SSB /CW... The second version had the warc bands & could have AM or FM added as a option. The last version was called the MK3 101zd ... I think , Had warc bands, AM/FM with optional board, And notch & APF filters. you could tell the latest one by the knobs.. The lager parts of the knobs was silver in color.. 73 john