Hamrla (1959, 1960) who investigated these beds in detail established on the basis of field data, results of drilling and historical records on coal mining the occurrence of two main coal horizons in the territory between Lipica and Lokve.
Hamrla (1959, 1960), ki je te plasti podrobno raziskal, je na osnovi terenskih raziskav, zgodovinskih podatkov o rudarjenju in raziskovalnih vrtin ugotovil, da se premog na ozemlju med Lipico in Lokvami pojavlja v dveh glavnih premogovnih horizontih.