What is the earliest possible reference for definition and basic properties of Clifford algebras associated to quadratic modules over a ringed space? The ringed space does not need to be locally ringed, but I am willing to assume that $2$ is invertible in the sheaf of rings if that helps. Searching mathematical reviews revealed a somewhat related paper: 

 - B. Auslander. The Brauer group of a ringed space. J. Alg. 4 (1966), 220-273. 

This paper develops some of the relevant math, but does not talk about the Clifford algebra. I would expect that there is some paper from around the same period defining the Clifford algebra for quadratic modules over a ringed space, but I could not find anything. 

I would also be interested if there are papers writing down the Clifford invariant mapping from the Witt group  to the Brauer group in the general setting of ringed spaces.