Is there any context you can provide? The clock piece for the ME109 was not just made for aircraft, so taking it provided Steinhoff with a time piece which may have been useful after being shot down and also a memento of his aircraft. Much more so than say an altimeter.

Ordered to - they also had to take their gun site. See here for what it did JUNGHANS BO-UK-1 FL23885 Blindfluguhr , EDIT This link is far more about the clock than the 1st its variations and the aircraft it was used in. Some nice pictures too. The Germans were and still are excellent precision clock/watch makers. As well as the fact they could use it. A clock needed for flight even with out the extra that has would be hard to produce and extremely valuable (not just in cost but in time and materials) Reverse engineered (we had some very clever chaps/chappesses dedicated to this) it might give us Brits a new technology, something about the capabilities of the plane and even production numbers. Somebody actually predicted the German armour figures based on a serial number stamped into a tank knocked out in France not long after the Normandy invasion. They were out by 5 when true numbers were worked out at the end of the war.

Aside from the practical reasons, an element of this would have derived from military tradition. Officers were supposed to destroy valuables and potential intelligence clues before abandoning a position. Artillerymen had to destroy or remove gun sights to prevent weapons being quickly put into use by the enemy.

The aeronautical rules would have derived from this tradition. Probably nobody would care if you just trudged back through 50 miles of desert or steppe without your radio etc, but the basic practice was still important to be followed at all levels.