  We show that the Deligne formal model of the Drinfeld p-adic halfplane
relative to a non-archimedean local field F represents a moduli problem of
polarized O_F-modules with an action of the ring of integers O_E in a quadratic
extension E of F. The proof proceeds by establishing a comparison isomorphism
with the Drinfeld moduli problem. This isomorphism reflects the accidental
isomorphism of SL_2(F) and SU(C)(F) for a two-dimensional split hermitian space
C for E/F.
