mis-matched parts

the other night i was cleaning a couple of my lugers and when i went to reassemble them i started to have trouble with the saftey and the trigger. they were just not fitting and i was about to get the hammer out and make it fit. well, i stopped, took a deep breath, then looked closely...yep, i had picked up the wrong parts from 2 different lugers. and true to the myth, the parts were not easily exchangable but slide in perfectly into the original lugers. so, i guess making a mismatched luger from spare parts is harder than thought to do. i guess those pparts were milled specific to the pistol afterall