I realize this reply is to a rather old question. However I may be able to add something of value to those who come here in the future with the same inquiry.
These were made by the Columbia Mint in (1979 and close thereafter) as another member posted, however they are actually 22K gold, exactly the same as the original coin was. This is for many reason, one of course keeping as true as possible to the coin being honored in miniature, but as in most jewelry, 24K is just so soft it damages very easily and even this approximate 5% 'other' metals can make a difference in this fact.
Consider that high grade stainless is 5% nickel and that changing the character of steel to a higher grade for some uses, the same as the 22K gold is about the highest used in other than 'pure' ingots.
I have a number of these miniatures. There were also Lincon Cents done in the same size also in 22K gold.
These are just for fun for me, not so much as an investment, but as a die hard coin'ie 'I just could not resist!' They came with necklace frames to hold them should you want to wear them around your neck or perhaps a charm bracelet.
They have certificates of authenticity with serial numbers such as 'AA 95000' printed on heavy weight 'Light Gray Paper' and they came with a small booklet called 'Gold Coinage Through The Ages', then below 'Saint Gauden's $20 Gold Piece' printed on a light yellow paper.
I have uploaded a black & white copy if your documents are missing, (serial numbers partially excluded of course.) You could create some replacements by printing on the colored paper I shared. Of course I would not try to create a Certificate of Authenticity, rather a copy of what 'they were' for your files.




