Are there no markings at all on the skillet bottom?
I was going to say CHF (chicago hardware and foundry), they did a lot of hammered pieces but I think all the ones I've seen have been marked with at least a size on the bottom. Lodge is another option, they did a lot of hammered items at times... your skillet isn't the 'ugly hammered'... its got the smaller pattern that looks better imho... but no heat ring... did lodge ever make a skillet without a heat ring? I know the 4in1 is smooth bottom but that is more of a chicken fryer than an actual skillet and chicken fryers always seem to be different, but the 4in1 is a similar hammered finish style to your skillet...