I also remember being pleasantly surprised to find out that the exchange rate was 10:1 between East and West German Marks; This wasn't apparent to us when we were looking at the price list displayed outside a hotel restaurant but once we clock this the prices looked VERY reasonable indeed so we proceeded to have a big feast!
Unfortunately a group / bunch (what is the collective noun for navigators - a mis-plot?) of navigator students weren't quite as clever. They changed some Deutsche Marks into
Mark der DDR and sat down to their feast. But when the bill arrived, it was clear that they hadn't changed enough money - so had to make good the balance with Dm, but at a rate of 1:1 rather than 1:10.....
On a slightly different tack some of the pedestrian crossings in Berlin had three lights by the push buttons, two red and one green. No one seemed to know the reason so we asked a policeman, as you do.
And woe betide you if you tried to cross the street either than 1. At an official crossing and 2. When the 'Grüner gehender Mann', not the 'Roter stehender Mann' was showing! If you tried anything else, there'd be much sighing, tutting and finger waving by the locals, because
'Befehl ist befehl - so sei es!'.