"from my higher callsign, meet us at the place where we stopped earlier, you know, the place with the rather nice roses outside? Usual tea-and-toast time, plus one hour"
Whether this sort of stuff ever actually fooled the Ruskies, who can say.
Nowadays used after a fashion to tell your loved ones when you're getting home off ops without breaking OPSEC - agree a date with them beforehand (not a birthday, anniversary or anything else the hordes of 'enemy spies' supposedly listening in will guess) and count back. So 'we'll be back three weeks before the date I told you'.