o) Allegation of public prior use 

In T 1583/21 the board did not consider it an unforeseen development in appeal proceedings – and so an exceptional circumstance – that an alleged public prior use, which would otherwise have been difficult and required great effort to find, had been discovered by chance as a result of a change of staff. The board, noting the claim that the prior-use rotor blade had been made publicly available in 2005, found that it should in principle have been possible to find it from then on. Besides, admitting a prior-use allegation shortly before oral proceedings was only rarely compatible with the principle of procedural economy.

See also T 2607/19 (prior use originating from a company belonging to the same group as the opponent).