What is the difference between an Non-Directional Beacon and a Compass Locator Beacon?
Normally "Compass Locator Beacons" were co-located with the outer marker for ILS approaches. A "compass locator beacon" is an NDB beacon specifically to drive the radio compass.

A radio compass was a lot simpler instrument than the ADF that worked off of the NDB beacons. Typically it just had a needle that pointed left/right to direct the pilot to turn towards the station. They operate on the same frequencies as ADF/NDB and can be tuned with an ADF receiver. 

Radio compasses used the old "loop antennas" that you see on old aircraft pictures. The pilot, co-pilot, or navigator would rotate the antenna by hand (the older radio navigation system required the pilot to turn, so rotating antennas were a step up) to be able to find the bearing to a particular station. 

ADF (the "automatic" part of the "automatic direction finder) eliminated the need to rotate the antenna to get the direction to the NDB. 

So to answer the question, the NDB and the compass locator beacon are technologically the same, it is the equipment in the aircraft that changed.

See NDB Nav History for more details