[will2]

Hi
I recently acquired an oil painting which I am considering to have it restored, as the varnish has darkened consirably.
In order to get an idea if this painting is worth restoring, I need to be able to identify the artist.
Please look at the attached pictures and perhaps you can identify the artist from his signature.
One shows a name marked on the back of the canvas, My the artist? Johnston seems to be the last name.
Any help would be appreciated.
Will