navy arms gunfighter series

[sweettooth]

Bought a navy arms gunfighter series silver backstrap . Beautiful piece  Raining today so cant shoot it yet . Had trouble getting it locally but Marshal Holloway got one for me . Feels a few ounces lighter than my brass frame uberti. MY QUESTION  The springs come up through the hammer a rectangular notch on the back .  and a small hole  in back of firing pin . My brass frame doesnt have this and I have not noticed it on any others.Navy arms installs wolff springs at the factory is this the reason ? Can anybody explain why the hammer has these and I have not seen them on any other piece ? Thanks Rick