Recently, through our purchases, we have had tons of 50s and 60s rockabilly and country boppers. Another sub-genre appears to be Hillbilly bop from the late 40s through the early 50s. Trying to put the 45's into the correct spots, sometimes is quite the the task. Personally, we base it on the beat, instrumentation, and to some extent lyrical content. Tons of this stuff coming down the pipeline, check it out!