Doug,
it may not have been quite clear, but in my earlier post I explained that the photo I posted shows a very good copy of an archaeological find; quite precisely dated to 1610 at Jamestown, VA, USA. One of the earliest English settlements in the US. The artifact survived in remarkable shape and it was simple to make a good reproduction with very little guesswork.
as to whether the springs were wrought iron- I don't know if that question has been answered and have been unwilling to do any destructive testing on the locks in my collection. I have made a reproduction using wrought iron, but wasn't able to get the spring to work properly. However, my lack of success doesn't rule out the use of wrought iron in better hands.
Peter