Only the very first 200 have a number on them.
The original run 5s (numbered and un-numbered) had a smaller and less pronounced American flag. The new ones, I believe, were done by Guy in house and the laser flag engravings are bigger and pop compared to the old ones as you can see in your pictures. Aside from that there are no other differences. The 5s are tanks and feel very different from the 4.7s. They also have more power are heavier and are taller.
Please take a photo and post it. I have seen patina and freckling not corrosion. But there's always a first time. I've handled Guy's corrosion test knives and wiped most of the rust off with steel wool and a wet rag. Did you buy this knife used or did you buy new?
The 5S is a great knife! But now I have a serious problem,When I open my 5S handle,I found a lot of rust!The rust and cannot be thoroughly cleared,I've heard that the rust of 3V steel will going deeper and deeper,and can't be spopped.