If we are to go by what the RB shows as a Blacklock, they have 1) an outside heat ring, 2) a raised size number on the top of the handle, as did early Lodge, 3) a molder's mark at 6 o'clock perhaps a little but not much larger than those seen on early Lodge, and 4) a rib on the bottom of the handle that is distinctively flattened off to about halfway down. There seems to be a tendency on the part of some to want to make any skillet with outside heat ring, raised size number on top and any raised molder's marks at 6 a Blacklock. I think it's still easier to definitely say what is not Blacklock than to say what definitely is. So, yours could be 1) an unusual example of a Blacklock, or 2) by an unknown foundry, not Blacklock, or 3) a pan made perhaps using a Blacklock skillet as a pattern.
If we had some skillets we felt strongly were Blacklock and could compare side-by-side with yours, we might be able to conclude yours is one also, but one that happens to have no molder's mark. The one thing that I keep looking at on yours, however, that's making me lean away rather than towards is the numeral 8 doesn't look like any I've seen on skillets purported to be Blacklock-- yours appears flat, and with the top and bottom of it the same size. The Blacklock and later Lodge raised numerals are more convex, if that's the right word, and the top of a numeral 8 is slightly smaller than the bottom.