3-phase connector
Is a BS6363 or CEE23 standard connector. It is now the standard connector for industrial/commercial use on this side of the 'Pond'. It is available in various voltage/current configurations, colour-coded for voltage. Red (as shown) corresponds to 380-440V. Blue is used for 240V (mainly single-phase). Yellow for 100-120V Single/3-phase (CTE). I (think) Green is 50V and purple is 24V, but not sure. I'm sure the relevant information must be on the 'net. Current capacities are 16,32,63, and 125 Amp. That one 'looks' to be a 32Amp.
There are also high current 'Camlok' connectors available in a similar housing (single terminal circa 500Amp)
Hope this helps
Dave T