  If the Universe consists of domains of matter and antimatter, annihilations
at domain interfaces leave a distinctive imprint on the Cosmic Background
Radiation (CBR) sky. The signature is anisotropies in the form of long, thin
ribbons of width $\theta_W\sim 0.1^\circ$, separated by angle $\theta_L\simeq
1^\circ(L/100h^{-1}{Mpc})$ where L is the characteristic domain size, and
y-distortion parameter $y \approx 10^{-6}$. Such a pattern could potentially be
detected by the high-resolution CBR anisotropy experiments planned for the next
decade, and such experiments may finally settle the question of whether or not
our Hubble volume is baryon symmetric.
