Arthur, this is a fascinating pictorial essay showing the evolution of the Delhi Durbar tiara as Queen Mary wore it. Thank you!
The only thing I find confusing is that Queen Mary looks older in that first picture from May 1911 than in several of the succeeding pictures. I think either it is the way the light fell across her hair, or she was greying early just before her 44th birthday, and dyed her hair for the Durbar and for awhile afterward. The picture is clearly documented by the newspaper date.
Like everything Queen Mary wore, the tiara in her hands was as adaptable as a coronet of that design could be. But it was because she had different jewels mounted on it, rather than the tiara being composed of pieces that could be worn separately. Thanks again for showing us what Queen Mary did with it.