staring at the pictures again, it seems clear to me that part of the oval is part of the orignal shoreline. I can see evidence of the original shoreline in both the top and bottom head lugs in the second picture. I might crank up a drawing program later to show you what I mean.

There were people that specialized in cutting lugs back in the day. There has been some discussion on the Classic Rendezvous mailing list about this regarding the U.K. builders. Of course, there is nothing saying that the builder didn't do it himself, this is the most common