The easy way to tell is to remove the slide and look at the color of the trigger assembly. The stock beretta trigger assembly is all black while the ltt is uncolored. Compare the trigger assembly in this video of stock vs ltt:
https://www.youtube.com/watch?v=YQum92bi5J8
Oh and think the stock px4 single action was 5lbs. So it probably does have the trigger assembly in it.