I believe it's a primary allocation for amateur use world-wide. I did check the League chart and found nothing to indicate that this is not so:
http://www.arrl.org/frequency-allocationsYou've got good ears Don. I sampled one second of the noise and counted the pulses. You are correct, it is a 50 cps source. I have received a number of emails indicating that this is OTHR emanating from either France or the Middle East. It does seem somewhat similar to a recording of OTHR made on the 30 meter band here:
http://www.youtube.com/watch?v=OD0mlxXbA0YRob W1AEX