Hello Mikee! DonĀ“t mess with your daggers!!!
When the head screw is "frozen" it is dangerous to open it by force because the tang might break or the thread might be worn down. Within seconds a nice hunting dagger can become a wrack. Even more it is possible that the grip itself is "frozen" on the tang and opening of the headscrew does not reveal the tang. There are several other dangers and afterwards the put together can develop a p-i-t-a...
And the untouched edged weapon will never be the same.
All I can say is that disassambling of an edged weapon should be carefully reflected and weighed.
Why do you want to know if there are any tang markings? Perhaps Baz69 can help you, I am sure he has already done some disassambling.
Regards,