It was marked :- second hand pickup cover + Ric o sound box, value $50, had a large Rickenbacker label on it and came in a medium jiffy bag. It didn't appear to have been opened.
Also it was quite light, shipping was only $6.
In fairness to the dealer, he did warn me that I might have to pay duty on it, and marked a lower price on the pro former.
At least I now know from your experiences that I was just unlucky and it is unlikely to happen to me again. I suppose they just pull something out for checking now and again.
Thanks for your help.