Need some help from the folks who know nails

The reason why I think you are right about the large nail is that it is machine made but hand headed. The early nail machines couldn't make the heads so someone did that by hand. The second one looks like it was sharpened and hand finished but that doesn't necessary mean its older. I read lots of old newspapers from the 1800's and I have seen advertisements for cut nails and hand forged nails together. I think that the hand forged nails were made for situations where they needed a nail that would bend before it would snap. The iron cut nails wouldn't do that.

here is a great video

https://www.youtube.com/watch?v=r8TUMXc8t4U

The tall nail in the second image down almost looks like a concrete nail. Is it square in cross section or rectangular? I don't know how long people have been using concrete nails and if some early ones were hand forged that way.

My house is from around 1849 and its nails look just like both of those. They go from large spike type ones around 4" long to little 2-inchers. The small ones always look sharper. They're all cut nails.

In my pre-detectoring days, it was always such a thrill to find a nail - "Ohhh, looky here! A square nail!" Now they are the bane of my existence I think the builders threw them around by the handful.