Thanks, I have read most of the references provided in the link. In Article 19.4 of the Totalization Agreement (1996) and Technical paper discussing this Agreement Social Security payments are specifically treated separately from the more general subject of Pensions, Annuities, etc. My reading would say that the US will treat all Social Security payments by either US (to Swiss National) or Switzerland (to US National) under the US Model. While not precisely the case, an example given uses the 85% rule (US Model) to calculate taxes on a Social Security payment.
