Painting of "Doble's Point"

I received an interesting email this week, as well as an attachment of this piece of artwork. The sender gave me permission to post onto this blog, to see if anyone knows anything about this image, or about the artist.

Here's the email:

My Name's Joseph Smith. I'm fascinated because I have an original watercolor (I suppose it could be a pastel) hanging on my wall of Doble's Point, Cape Cod signed by Rattigan (?).

In doing research, I came across a postcard for sale of almost exactly the same scene...but by someone different. I've stumbled across your blog site and have gleaned a little about the history of the area. I'm just wondering about this painting....and its artist. Any thoughts??

 Thanx, Joe Smith

I've already written back to tell him where the scene was painted, etc., but if anyone has further information the man would appreciate it. Or especially if you recognize the artist's name? You can post answers here in the comment section and I will orward to make sure he sees them. Or call me if that's easier.

(I would think the art must be from the first half of the 1900s to be labeled "Doble's Point" instead of "Old Mill Point.")

Thanks - and spring is just around the corner!