Webley Mk1 Slant Grip Prototype?

[Diabolical]

Good afternoon, I am interested to see if anyone can shed possible light on this recent acquisition. It is a Webley Mk1 pistol with no markings other than a serial number of 47911 in the usual position and 911 on the front lug. The grip frame has been machined across and a new frame with slant grip angle has been bolted up to it with perfectly matching contours (machined at same time as the rest?). The patina of the modified frame also matches perfectly the rest of the pistol so I assume was contemporaneous. The grips have been machined from aluminium flat with great care and attention to rounding off and matching both sides.
Here is a link to a set of photos

https://www.flickr.com/gp/164729373@N04/LXN5Mn

Any thoughts greatly appreciated!