Hi Eric,
There were different frame lengths in variations of Lugers. There has been discussion on the board about identifying those. Here is Ron's
"Early Frame Tutorial".
Each Luger was hand fitted. That's why they are numbered. So that all the parts of a hand fitted Luger go back. For that reason, they are not strictly interchangeable. Close, but not precise - and that precision is needed for a correctly operating pistol.
Marc
__________________

Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.