Changes made by 77/374/EEC: Commission Decision of 13 May 1977 allowing admission free of Common Customs Tariff duties of scientific apparatus described as 'Lock-in-Amplifier' PAR, model 186 A with internal oscillator, PAR, model 186 A/99/97, optional
EU Decision 1977/374
No changes made by 77/374/EEC: Commission Decision of 13 May 1977 allowing admission free of Common Customs Tariff duties of scientific apparatus described as 'Lock-in-Amplifier' PAR, model 186 A with internal oscillator, PAR, model 186 A/99/97, optional are recorded.
From legislation.gov.uk's record of changes, the official one: see it there.