All About Pocket Knives

Found a Schrade auto at my friendly local antique shop the other day.Beautiful scales;blade has been sharpened a bit;locks nicely but the spring was broken.For $32 I took it home figuring to replace the spring.
Had an identical(or so I thought)one that I bought many years ago that had a small piece of the scale in front of the button missing;causing it not to lock properly.I thought the lever part of the button was broken and was going to repair it when I found a parts knife.Blade is nice and full and there is a small piece missing from the opposite side scale too.
While inspecting them both to see the feasibility of swapping the spring into the new acquisition,I noticed something a bit unusual:Although the tang stamps seem to be identical except for a slight location difference,the patent dates on the back of the tangs are not only different but one is in very small letters.
The one I got yesterday has larger letters and the patent dates are:Dec.21 '09-Sept 13 '10-and June 6 '16 whereas the older one has the dates:Feb 13 '05(or '06;it is hard to read);Feb 26 '07-Sept 13 '10.
So my question is this:Does this mean the latter was made prior to 16 and after 1910?
I'm also curious as to what modifications were made to require all new patent dates.The knives look for all intents and purposes identical taking into consideration blade wear and jigging differences.
I've enclosed several pictures for your inspection and apologize for the blurriness of a couple.Any info or comments are welcomed.

I think some of those later patents had to do with improving upon the originals, for example the June 1916 patent has to do with developing a stiffer spring geometry and providing more clearance under the spring to prevent an accumulation of debris underneath it from weakening the action. You might find that the back "springs" on these knives have slightly different shapes internally. Possibly this will result in different tang shapes and kick lengths as well?

Eric

Thank you for the response.Upon examining them once abain I do detect one difference in the early and late versions:On the earlier version if you look closely at the bolster near the bottom you will see a pin there.On the later version the pin was apparently removed.

Nice press buttons, knife7!