In 1948/49, when the first anodised badges were being proposed & made, the designers were having problems with the bonding agent which fastened the slider to the badge. This went on for years. By 1953/54 Gaunts & Dowlers experimented with the brass slider. What they did as part of the design is leave an aluminium post coming from the badge. Then they would fit the slider over it & press it down; this would give it the rivet effect. I have 2 sealed patterns sealed in 1954, but by 1955, these had been cancelled. In 1955 a new bonding agent was devised for use in the nuclear power industry. This was so strong it solved the problem of the bonding of slider to badge.
Peter