Some corrections concerning the historical evaluations of the slag analyses made on samples from the layers in a Romano-Barbarian site at Presov-Pavlovicovo Square, and from early medieval Nemcovce are given. Slags rich in fayalite must not be an evidence for using inferior quality iron ore; they may attest to a reaction with the furnace lining as well as a better performed smelt. A call for broader comparative studies is expressed, especially in the process of evaluation of analytical results, since the body of recent research produces a steadily increasing bibliography. A very limited selection of references is added. -- AATA