Physikalisch-Technische Bundesanstalt (PTB) brings expertise and experience in the development and metrological application of metallic and semiconductor single-electron-based current source and detector devices developed over about two decades, all fabricated on-site. PTB also has outstanding experience in high-accuracy current measurements, as well as in the development and metrological application of cryogenic current comparator systems. Particularly the ultra-stable low-noise current amplifier (ULCA) is a PTB development. PTB also has access to Josephson-voltage and quantum-Hall-resistance standard systems. Recent scientific milestones are the closure of the quantum metrology triangle with the electron-counting capacitance standard experiment with uncertainty 1.7 parts in 106 (2011), the demonstration of in situ error accounting with single-parameter tuneable-barrier pumps involving metallic single-electron transistors (2013-2014) and the validation of current quantisation in a single-parameter tuneable-barrier pump with world-record accuracy of 2 parts in 107 (2015). All these have been achieved within iMERA-Plus JRP T1-3 REUNIAM and EMRP JRP SIB07 Qu-Ampere, both coordinated by PTB.