As I have read some lugers have the hold open and some dont. I have an early 1900 AE SN 8372 which has a hold open latch, and a couple other 1916 and 1917 which also have the hold open latches.
Seeing that the AE was one of the early versions and it has it, what vintage and contracts didnt have them
these are side by side pics of my 1900 AE and my 1916 shooter. They pretty much look the same with little differences in thed frame itself.