My father-in-law handed me a beautiful 1937 Elgin pocket watch that was his father's.  I was able to get it apart, with a bit of difficulty.  The mainspring would not let down.  I could not get any movement of the ratchet wheel.  So, I removed the click, while holding the crown.  Nothing!  I had to coax the ratchet wheel to move using a probe on the teeth.  Then I was able to let it down.  Once I got the barrel open, it looks like old oil had essentially cemented the mainspring coils in place.