This might be a repeat, but let me take a stab; 1940 equals the year it was made, 1940, while the 42 means Mauser, who made the arm.
The serial number and then the "i" is the suffix of the gun.
The 122 and the Eagle 37 are proofs and acceptance markins, as is the 655.
I had a 1940 / 42 just like this for a while. It is a nice WW2 gun.
Jan Stills Third Reich Lugers is the best on WW2 Lugers and information can be obtained from this address:
mailto:jcstill@ak.netjcstill@ak.net</a>
Ed