my boss just bought a like NIB model 92 9mm.

we were looking at it and when the slide is open (as if last round had fired out of the clip) and the safety ON, you can push the safety OFF and the slide closes and the hammer falls.  this seems abnormal to me, but i shoot only glocks so i didn't no for sure.

any help appreciated greatly...brad

The safety on the 92 is designed to drop the hammer when the slide is forward.  When the slide is locked back with the safety is on and the slide is released, the hammer will fall on the firing pin block.  If the hammer is falling with the safety off when the slide is released, you should be concerned.

I'm not sure I follow you.  Are you saying that activating the safety with the slide locked backed causes the slide to release or just that the hammer falls when the slide is released?

You'll notice that if you cycle the action by hand with the safety activated the hammer stays in the cocked position until the slide is fully closed and then the hammer falls forward.  

You'll also notice that if the slide is activated the rear of the firing pin is rotated up and away from the hammer so there is no way that it can be hit by the hammer and this is completely safe.

If you pull the slide off and look at the bottom of it while moving the safety lever back and forth you'll see that the bottom of the safety is exposed but has a cut out so that it fits flush when the safety is off.  There is a matching cam on top of the frame that drops the hammer if it is pressed down.  When the safety is off the cam isn't pressed down and it stays in the cocked position.  When the safety is rotated the exposed portion under the slide pushes down on the cam and de-cocks the hammer.  The bottom of the safety doesn't hit the cam until the slide is all the way forward and that's why the hammer stays cocked until the slide is released.  

An interesting piece of trivia:  The Beretta works well with silencers so the Navy SEALs ordered a special run of 92 Brigadier (heavier slide) pistols a couple of years ago and they ordered them with the cam on the frame removed so that the pistols can be carried cocked and locked.  

It could be a weak slide stop spring, and the pressure of pushing the safety up is causing the slide to go forward (dunno, maybe?).

I'm about a month late on this, but I thought I'd throw in my 2 cents.  It's perfectly normal... don't worry about it.  The hammer is designed to fall when the safety is on.  In fact, if you look in the manual, that's how they recommend you drop the slide on a live round (with the safety on, so the hammer falls with every safety engaged)