Nuclear magnetic ordering in silver has been investigated by the low-field NMR technique using an rf SQUID. Spin entropies down to 0.50 · R ln 2, corresponding to polarizations up to 78%, were obtained. An indication of antiferromagnetic ordering was observed in the static magnetic susceptibility, which showed clear saturation at the beginning of warmup after cooling to T<1 nK by adiabatic demagnetization to B=10±5 µT; the critical entropy of the transition was found to be Sc=(0.60±0.04) · R ln 2. The NMR absorption increased in the ordered state at frequencies around 75 Hz. Remnants of this increase were observed in the paramagnetic phase as well. The feasibility of experiments at negative spin temperatures was demonstrated by a quick reversal of the external magnetic field.