Is it similar to this? (I borrowed this image from cindysantiquequilts.com/dynapage/IP315.htm)
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Other people might have more insight into this, but I have seen pictures of quite a few Featherweights with this type of label, including black ones. I'm not sure what the A would stand for; the J in this picture is because it was made in Canada, and the K often seen means made in Scotland.
I've never heard of a Featherweight clone, so I suspect it's genuine if it looks right in all other ways. Could you post a photo of it? People might be able to give you more input then.