I reread my reply post and it does look like I am confirming that the cross is an original, when what I was really trying to tell jbm that you stated "original" and didn't realize that it was a little tongue and cheek in your post.
No, I don't think the cross is an original. With the yellowing color, it looks more like German silver or possibly brass(?). Some of the less reputable Traders were known to use brass, copper and other metals and rub Mercury (Quick Silver) to make the NA tribes think that the item was real silver, but it is said, that most tribes caught on to this fraud quickly and demanded silver.
JMHO
Rick