I think you buy "a lot of a shotgun" for $500 dollars, either if it is a 408 or 409 model.
I wish I could find such a bargain this side of the border.
Chokes are more like imp mod (0.027") and full (0.039")and 1,350 is the barrels weight in GRAMS (not Kg) Europeans use the comma (,) for decimal point (.)
I am also pretty sure that the firing pins are integral (same piece) with the hammers in this shotgun.
The "untouched" screws talks fine about what is inside (a clean mechanism!).

Enjoy!

Best,

Jose M. Fernandez