You should have been around in the 60's and 70's when 121.05 was in use daily for radar talkdowns to half-a-mile from touchdown! [Tower was 122.30 in those days].
If memory serves correctly, the 'new' frequencies came into use with the new Tower back in the Sixties. Initially 123.75 was a combined Tower and Approach frequency with Radar on request on 121.05. The separate Tower frequency of 120.3 was allocated but not used until a bit later.
In the old Tower, TWR/APP was 122.3 and Radar was 130.2