Amongst the many gifts to honour her Golden Jubilee, Queen Victoria received a long diamond chain with a crown and the years 1837 and 1897 in diamonds from her younger children and their spouses. These were the Duke and Duchess of Saxe-Coburg and Gotha (Edinburgh); the Duke and Duchess of Connaught; Prince and Princess Christian; Princess Louise and the Marquess of Lorne; Princess Henry of Battenberg and the Duchess of Albany.
In her diary Queen Victoria recorded that she wore the chain for the drive through the city and the Thanksgiving Service.
In a photo taken on the day, a little part of the chain can be seen on either side of the Queen's neck.
Unfortunately, Queen Victoria did not record which brooch she wore but, as it is obviously a cabochon, I wonder if it might be the star sapphire brooch set in diamonds which Queen Alexandra gave her. Without additional information, I doubt if this can be verified.
Thank heavens for the sparkle of diamonds otherwise it would be impossible to identify the chain.