Power switch cufflinks.
These are unusual as the front plate (whole button switch) turns on a screw fitting and can be taken off the back. They screw quite a long way together, which may aid in pushing the cuffs closer together, if required.
Large fronted cufflink.
Plated cufflink with screw fitting
Dimensions (Diam x H): 16mm x 11mm (approx.)
Weight per cufflink: approx. 11.14g (heavy)
Size = x mm (W x H)