ISO 19650 term depends on where in the hierarchy the employer is located.
The BS EN ISO 19650‑2 appointing party (A) is the equivalent of the PAS 1192‑2:2013 top‑level employer
Lead Appointed party (Tier 1)
Lead appointed party is not the same as design lead or construction lead in PAS 1192‑2. See 9.5.4.
The BS EN ISO 19650‑2 lead appointed parties (B) are the equivalent of the PAS 1192‑2:2013 Tier 1 lead supplier. PAS 1192‑2:2013 only suggested two Tier 1 lead appointed parties (lead suppliers)
Tier 1 Contractor is typically the Lead Appointed party or Appointed party by the client, at the same time the Tier 1 Contractor can become an employer to Tier 2 sub-contractors, therefore becoming the Appointing party