Panel a: rate of 3BPUs as a function of time. The dotted lines correspond to the mean rates over a 10 Gyr period. Panel b: normalised distribution of the estimated apparent age for the 3BPU merger products. The apparent age is determined by mapping the Helium-core mass fraction of the primary at the time of the merger to the corresponding age a normal star with the mass of the merger product would be with an identical Helium-core mass fraction. Panel c: normalised distributions of the total masses of the 3BPU merger products. For all panels, binaries originating at 0.1 pc are shown in black, and those from 0.3 pc are in red.