Thanks for the comments. Yes, the grips are secured each side with a screw. There are no machining marks visible on the grip frame, and the front end of the trigger guard is 'keyed' into the original frame very precisely. The rounding off of the edges of the grip frame all around match exactly that of what remains of the original frame, which as a model engineer myself would not have been an easy operation. It is a fact that there is no provenance with this pistol hence why I posted on here for any views and information. One point that has not been covered thus far though, why are there no patent markings on it? What is the likelihood of a Mk1 with that serial number having etched markings on it that have long worn off...