Yes, that would be a 15-30. The needlebar site is a good start, but I disagree strongly with their saying that the 15s made in Kilbowie use the same numbering system. I haven't compared all of them, but I know that the 15K30 is not the same as a 15-30. You don't have to worry about that as yours was made in Elizabeth, New Jersey.
Probably, the cabinet was exchanged for something smaller, when it was electrified.
Your decals look better than mine -
Janey - Neat people never make the exciting discoveries I do.