You will find police guns without sear safeties, but never find a military with a sear safety.
The only way to tell if it is a police and there isn't a sear safety is either a police unit marking or during the nazi times you might see an eagle L or the like.
As said above, read the FAQ and it talks about sear and magazine safeties.
FAQ
http://forum.lugerforum.com/showthread.php?t=13121
Ed